Light-emitting device with improved flexural resistance and electrical connection between layers, production method therefor, and device using light-emitting device

ABSTRACT

A light-emitting device includes a pair of light-transmissive insulator sheets disposed opposite to each other and two types of light-transmissive electroconductive layers disposed on a common one of or separately on one and the other of the pair of light-transmissive insulator sheets, and at least one light-emitting semiconductor each provided with a cathode and an anode which are individually and electrically connected to the two types of the light-transmissive electroconductive layers. The electrical connection and mechanical bonding between the members are improved by a light-transmissive elastomer which is between the pair of light-transmissive insulator sheets. A method in which a light-emitting semiconductor element and a light-transmissive electroconductive member are subjected to vacuum hot-pressing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. application Ser. No. 15/802,703,filed Nov. 3, 2017, which in turn is a continuation of U.S. applicationSer. No. 14/771,816, filed Sep. 1, 2015, which in turn is the NationalStage of International Application No. PCT/JP2014/058747, filed Mar. 27,2014, which is based on and claims the priorities of JapaneseApplication No, 2013-069988, filed Mar. 28, 2013, and JapaneseApplication No. 2013-069989, filed Mar. 28, 2013, of each of which thebenefits are claimed herein and the entire disclosures of each areincorporated herein by reference.

FIELD OF THE INVENTION

The embodiments relate to a light-transmissive light-emitting deviceequipped with light-emitting elements, its production method, and anapparatus using the light-emitting device.

BACKGROUND OF THE INVENTION

A light-transmissive light-emitting device is formed by electricallyconnecting electrodes disposed on light-emitting elements tolight-transmissive electroconductive layers on a substrate. As theconnection method, the wirebonding method has been used conventionallybut is not desirable as a connection method for use in a devicerequiring translucency, such as a touch panel or a light-emittingdevice.

On the other hand, Patent documents 1-5 disclose methods not using thewirebonding method for connecting light-emitting elements in alight-emitting device.

Light-transmissive light-emitting devices disclosed in Patent documents3-5 are useful for achieving a curved shape which cannot be realized byconventional nonflexible light-transmissive light-emitting devices.

PRIOR ART DOCUMENTS Patent Documents

Patent document 1: JP-A 11-177147

Patent document 2: JP-A 2002-246418

Patent document 3: JP-A 2007-531321

Patent document 4: JP-A 2009-512977

Patent document 5: JP-A 2012-84855.

SUMMARY OF THE INVENTION Problems To Be Solved by the Invention

However, as for a flexible light-transmissive light-emitting device usedat windows or exterior of, e.g. a car, a train, a vessel, an airplane,etc., such a light-transmissive light-emitting device is required tosatisfy reliabilities under a wide temperature range and underapplication of repetitive stresses. Unless reliabilities are satisfiedso as to clear the above-mentioned repetitive environmental conditionsand operating conditions, the use of a flexible light-transmissivelight-emitting device will be restricted extremely. From suchviewpoints, the light-emitting devices disclosed in Patent documents 3,4, and 5 lack sufficient reliabilities and the practical utilitiesthereof were limited.

Moreover, the light-emitting devices disclosed in Patent documents 3, 4and 5 are accompanied with problems that, under application of apressure during the production thereof, electrode edges formed on thelight-emitting device, the concavities and convexities formed on theelectrodes, a level difference at edges of an active layer and thedevice substrate, etc., are abutted against the light-transmissiveconductive layer of a light-transmissive electroconductive member, thusbeing liable to result in a crack in or breakage of thelight-transmissive conductive layer and cause disconnection leading to alowering in production yield and an increase in production cost.Furthermore, since the light-emitting devices disclosed in Patentdocuments 3, 4 and 5 are accompanied with fine cracks in thelight-transmissive conductive layer of light-transmissiveelectroconductive member during the production thereof in many cases,thus being liable to cause lighting failure in case of being bent orunder application of a heat cycle, even if they are lighting immediatelyafter production.

Furthermore, since the light-emitting devices disclosed in Patentdocuments 4 and 5 are insufficient in contact between thelight-transmissive conductive layer and the LED electrodes, they havepoor resistance to bending and leave a problem in reliability afterapplication of heat or thermal cycles.

An embodiment of the present invention has been developed in view of theabove-mentioned situation, and an object thereof is to provide alight-emitting device which is excellent in flexural resistance or inheat cycle characteristic during production or in use, or capable ofpersistent lighting in resistance to flexure or application of heatload, a process for production thereof and an apparatus using thelight-emitting device.

Means for Solving the Problems

The inventor tested light-emitting devices including alight-transmissive elastomer disposed between a light-emitting diode(LED) chip as an example of a light-emitting element and alight-transmissive electroconductive layer, and has discoveredinfluences of a ratio of an area of presence of the light-transmissiveelastomer to an area of the electrode of the LED chip, and a proportionof the light-transmissive elastomer present at concavities of unevennessof the electrode layer on the flexural resistance of the light-emittingdevice. The inventor has also discovered influences of the ratio of thearea of presence of the light-transmissive elastomer between the LEDchip and the light-transmissive electroconductive layer to the electrodearea of the LED chip, and the proportion of the light-transmissiveelastomer present at concavities of unevenness of the electrode layer onthe heat-cycle resistance of the light-emitting device. The term“flexural resistance” used herein refers to a resistance todeteriorations, such as crack, breakage and disconnection, when a filmor sheet-like product or material subjected to a flexure (bending) or arepetition of flexures at a certain curvature radius.

A light-emitting device of this embodiment has been developed to solvethe above-mentioned problem, and comprises:

-   -   a pair of light-transmissive insulator sheets each equipped with        a light-transmissive electroconductive layer, or a pair of a        light-transmissive insulator sheet equipped with        light-transmissive electroconductive layers and a        light-transmissive insulator sheet free from a        light-transmissive electroconductive layer, disposed opposite to        each other so as to form a region between the pair,    -   at least one light-emitting semiconductor element each provided        with a cathode and an anode which are individually electrically        connected to one and the other of said light-transmissive        electroconductive layers, and a light-transmissive elastomer,        respectively disposed between the pair of light-transmissive        insulator sheets so as to fill the region in combination,    -   wherein the light-transmissive elastomer is at least partially        present in the interface between the cathode and anode,        respectively, of the light-emitting semiconductor element and        the light-transmissive electroconductive layers, and    -   the light-transmissive elastomer is also filled in concavities        of the cathode and anode surfaces. Herein, the “light-emitting        semiconductor element” refers generically to an element wherein        a luminescence layer comprising a semiconductor causes        luminescence under application of an electric field (current)        formed between a pair of electrode electrically connected with        the luminescence layer, which may be represented by a        light-emitting diode (LED), but not restricted thereto and can        also include an organic EL device and a laser diode.

A process for producing a light-emitting device according to anembodiment has been developed to solve the above-mentioned problem, andcomprises:

-   -   disposing a light-transmissive elastomer between an electrode        surface of a light-emitting semiconductor element and a surface        of a light-transmissive electroconductive layer of a        light-transmissive electroconductive member, and    -   then subjecting the light-emitting semiconductor element and the        light-transmissive electroconductive member to vacuum hot        pressing at a temperature which is in a range of from 10° C.        below the Vicat softening temperature to 30° C. or 20° C. above        the Vicat softening temperature, respectively, of the        light-transmissive elastomer.

An apparatus according an embodiment has been developed to solve theabove-mentioned problem, is characterized by including theabove-mentioned light-emitting device, and may representatively providea display apparatus or an illumination apparatus.

Effect of the Invention

According to an embodiment of the present invention, there are provided:a light-emitting device that includes a light-transmissiveelectroconductive member comprising a light-transmissiveelectroconductive layer held on a light-transmissive insulator sheet, ofwhich the light-transmissive electroconductive layer can hardly cause acrack or a fracture, that is excellent in flexural resistance orheat-cycle characteristic and that can hardly cause bubbles remainingtherein, a process for production of the light-emitting device; and anapparatus including the luminescent device.

More specifically, the light-emitting device (or an apparatus includingit) is characterized in that the sandwiching of a light-transmissiveelastomer between an LED chip and a light-transmissive electroconductivelayer, followed by hot pressing under vacuum, is effective for improvingthe adhesion between the light-transmissive elastomer and thetransparent electroconductive member and preventing the occurrence ofcrack or breakage in the light-transmissive electroconductive layer, andalso for partial intrusion of the elastomer between the electrodesurface of the LED and the light-transmissive electroconductive layer toenhance the mechanical junction by the elastomer therebetween. As aresult, even when the light-emitting device is subjected to severebending or application of a heat cycle, the light-transmissiveelectroconductive layer does not readily cause a crack or a breakage,and a reliable electrical connection between the light-transmissiveelectro-conductive layer and the LED chip electrode is ensured, to allowa persistent lighting under such severe conditions.

Moreover, as the elastomer is processed under vacuum while preventingthe melt-fusion of the elastomer causing a low-viscosity state, theremaining of air bubbles in the resultant light-emitting device isprevented. If the hot pressing is performed under an atmosphericpressure or a slight degree of reduced pressure, air bubbles remainespecially in the circumference of the LED chip within the resultantlight-emitting device and the air bubbles compressed during the hotpressing are liable to swell after the hot pressing, thus being furtherliable to cause a peeling between the LED chip electrode and thelight-transmissive electroconductive layer. Furthermore, if theelastomer inserted between the LED tip and the light-transmissiveelectroconductive layer is melted or in a low-viscosity state at thetime of the hot pressing, the LED chip is liable to be displaced orinclined to cause an electrical connection failure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a light-emitting device of a firstembodiment.

FIG. 2 is a partial enlarged view of FIG. 1 .

FIG. 3 is a partial enlarged view of a part A1 in FIG. 2 .

FIG. 4 is an example of cross-sectional scanning electron microscopephotograph of the light-emitting device of the first embodiment.

FIG. 5 is an example of scanning electron microscope photograph showinga surface state of a first electrode layer 15A of LED chip 10 afterpeeling between the first electrode layer 15A and a firstlight-transmissive electroconductive member 20A.

FIGS. 6A to 6C show surface states of a first electrode layer 15A of LEDchip 10 after peeling between the first electrode layer 15A and a firstlight-transmissive electroconductive member 20A in a light-emittingdevice of Example 3 according to the first embodiment; among which FIG.6A is a scanning electron microscope photograph, FIG. 6B is an elementalmapping photograph for carbon according to energy dispersion-type X-rayanalysis (EDX), and FIG. 6C is an elemental mapping photograph for tinaccording to EDX,

FIG. 7 illustrates a production process for a light-emitting device of afirst embodiment.

FIG. 8 illustrates Production Example 1 for a light-emitting device.

FIG. 9 illustrates Production Example 2 for a light-emitting device.

FIG. 10 is a partial enlarged sectional view of a light-emitting device90 prepared by Production Example 1.

FIG. 11 is a partial enlarged view of a part B1 in FIG. 10 .

FIG. 12 is a cross-sectional photograph of a light-emitting device 90prepared by Production Example 1.

FIG. 13 is a cross-sectional photograph of a light-emitting device 90Aprepared by Production Example 2.

FIG. 14 is a sectional view of a light-emitting device of a secondembodiment.

FIG. 15 is a sectional view of an LED chip for a light-emitting deviceof the second embodiment.

FIG. 16 illustrates a production process for a light-emitting device ofthe second embodiment.

FIG. 17 is a schematic cross section of an example of a one-faceelectrode-type light-emitting device containing a bump electrode.

FIG. 18 is a schematic cross section of an example of a two-faceelectrode-type light-emitting device containing a bump electrode.

FIG. 19 is a side view showing an example shape of Au bump formed on apad electrode.

FIG. 20 is a plan view showing an example of disposition of bumpelectrodes in a one-face electrode-type light-emitting device.

DETAILED DESCRIPTION OF THE INVENTION

In a light-emitting device according to an embodiment, alight-transmissive elastomer is disposed between an electrode surface ofthe LED chip and a light-transmissive electroconductive layer of alight-transmissive electroconductive member, the light-transmissiveelastomer intrudes into gaps between concavities of unevenness on theLED chip electrode and the light-transmissive electroconductive layer,and the electrode layer of the LED chip and the light-transmissiveelectroconductive layer are electrically connected.

Incidentally, the sizes, such as thickness, width and distance,described herein are all based on values measured after standing for atleast 1 hour in a room at a temperature of 20° C.±2° C. by means of anon-contact method, e.g. optically, or by comparison with a calibratedstandard length after measurement through an electron microscope or anoptical microscope.

The light-emitting device of an embodiment, as a result of the formationof a light-transmissive elastomer layer of a relatively high storagemodulus at gaps between the LED chip electrode surface and thelight-transmissive electroconductive layer surface, is provided withlittle liability of causing a crack and a fracture in thelight-transmissive electroconductive layer even when subjected to asevere bending or application of a heat cycle to retain a sufficientcontact between the light-transmissive electroconductive layer and theLED chip electrode layer, thus ensuring a reliable electrical connectiontherebetween and persistent lighting.

Luminescent devices of embodiments are described in more detail withreference to drawings. A light-emitting device of a first embodiment isdescribed first.

Luminescent device First Embodiment

FIG. 1 is a sectional view of an essential part of a light-emittingdevice according to a first embodiment.

A light-emitting device 1, includes: an LED chip 10 including an LEDbody 11 and first and second electrode layers 15 (15A, 15B) formed on afront and a back face, respectively, of the LED body 11; first andsecond light-transmissive electroconductive members 20 (20A, 20B)respectively covering the LED chip 10 and including transparentsubstrates 21 (21A, 21B) and first and second light-transmissiveelectroconductive layers 25 (25A, 25B); and a light-transmissiveelastomer layer 30 joined to a circumference 13 of the LED chip 10 andalso to the light-transmissive electroconductive layer 25A of thelight-transmissive electroconductive member 20A and thelight-transmissive electroconductive layer 25B of the light-transmissiveelectroconductive member 20B.

In short, the light-emitting device 1 is formed by sandwiching the LEDchip 10 with two sheets of the light-transmissive electroconductivemembers 20A and 20B and joining the LED chip 10 and thelight-transmissive electroconductive members 20A and 20B with thelight-transmissive elastomer layer 30.

LED Chip

FIG. 2 is a partial enlarged view of FIG. 1 . FIG. 3 is a partialenlarged view of a part A1 in FIG. 2 . FIG. 4 is an example ofcross-sectional scanning electron microscope photograph of thelight-emitting device of the first embodiment. In FIG. 4 , a referencenumeral 95 refers to a resin for fixing the light-emitting device 1 asan objective sample for cross-sectional observation thereof and is not acomponent of the light-emitting device 1.

The LED chip 10 has a structure including an LED body 11 having a(laminate) layer structure corresponding to a semiconductor luminescencelayer of an LED, and an electrode layer 15A as a first electrode layerand a second electrode layer 15B as a second electrode layer formed onboth faces of the LED body 11.

Referring to FIG. 2 , the LED body 11 has an N-type semiconductor layer42 and a P-type semiconductor layer 44 on a semiconductor substrate 41comprising GaAs, Si, GaP, etc., and also a luminescence layer 43 formedbetween the N-type semiconductor layer 42 and the P-type semiconductorlayer 44.

The surface of the semiconductor substrate 41 and the surface of theP-type semiconductor layer 44 constitute surfaces 71 of the LED body 11,respectively. Here, the surface of the semiconductor substrate 41 iscalled a first face 71A of the LED body 11 among the surfaces 71 of theLED body 11, and the surface of P-type semiconductor layer 44 is calleda second face 71B of the LED body 11. The second face 71B is on thelight-emitting side 85 of the LED chip 10. It is possible to form atransparent electrode layer on the surface of P-type semiconductor layer44. In this case, this transparent electrode layer provides a secondface 71B.

The electrode layer 15A is formed on the first face 71A of the LED body11, i.e., the surface of the semiconductor substrate 41, and forms asubstrate-side electrode layer which is electrically connected withN-type semiconductor layer 42 via the semiconductor substrate 41. Theelectrode layer 15B is formed on the second face 71B of the LED body 11,i.e., the surface of P-type semiconductor layer 44, and forms alight-emitting-side electrode layer electrically connected with theP-type semiconductor layer 44. The electrode layer 15B as thelight-emitting side electrode layer is formed on a side closer to theluminescence layer 43 than the electrode layer 15A. In addition, it ispossible to dispose a reflective film on the semiconductor substrate 41surface.

The electrode layer 15A (cathode in this example), as a substrate-sideelectrode layer, may comprise, e.g. Au, and the thickness is usually0.1-2 μm, preferably 0.3-1 μm. The electrode layer 15B (anode in thisexample) as a light-emitting-side electrode layer, may comprise, e.g.Au, and the whole thickness thereof (i.e., a height of the side wall 17of the electrode layer 15B) is usually 0.5-20 μm, preferably 1-10 μm.

The electrode layer 15A (as the substrate side electrode layer) isformed substantially all over the first face 71A on the side of thelight-transmissive electroconductive member 20A among the surfaces 71 ofthe LED body 11.

The electrode layer 15B (the light-emitting side electrode layer) isformed in a smaller size than, e.g. 10 to 30% of, the second face 71B ofthe LED body 11 so that luminescence is not substantially obstructed. Inother words, the electrode layer 15B of the LED chip 10 is made smallerin areal size than the second face 71B of the LED body 11 on which thiselectrode layer 15B is formed. Incidentally, a transparent electrodelayer can be present between the LED body 11 and the electrode layer15B.

Generally, unevenness is formed on the first face 71A of thesemiconductor substrate 41 on which the electrode layer 15A is formed,and as a result, a corresponding unevenness 45 is given to the electrodelayer 15A laminated on it, thereby an improvement in connection with acontiguous layer is achieved. The unevenness 45 on the surface of theelectrode layer 15A is formed of concavities 46 and concavities 47 ofthe electrode layer 15A.

Generally, the unevenness 45 of the electrode layer 15A is formed inorder to improve the adhesion with the contiguous electroconductivelayer, and a surface roughness Ra (a measuring method thereof ismentioned later) of usually 1-5 μm is given thereby. Incidentally, asurface roughness Ra of unevenness (not shown) of the surface of theelectrode layer 15B is usually 0.1-1 μm.

The unevenness may be formed as a succession of concavities andconvexities, or may be given by intermittent formation of concavitiesand/or convexities as by embossing. The surface roughness Ra of theunevenness of the surface of the electrode layers 15A and 15B can be 0.1μm-10 μm.

The structures and materials of the semiconductor substrate 41, theP-type semiconductor layer 44 and N-type semiconductor layer 42 of theLED chip 10, and the characteristics of the LED chip 10 are not limitedas long as desired luminescent performance is acquired. Moreover, it isalso possible that the semiconductor substrate is a P-type or N-typesemiconductor and/or the P-type semiconductor layer 44 and N-typesemiconductor layer 42 are disposed upside down. However, it isdesirable that the semiconductor substrate has a semiconductor typeopposite to that of a semiconductor layer contiguous thereto, in view ofthe luminous efficiency.

The LED chip 10 may comprise an LED chip emitting, e.g. red or orangelight, but may comprise an LED chip emitting another color of light or acombination of the LED chips emitting plural luminescence colors.

The LED chip 10 may ordinarily have a thickness (height) of, e.g. 90-290μm, while it is not restricted in particular. Moreover, although thesurface size of the LED chip 10 may naturally change variously with arequirement as a display element (unit) for constituting the whole areaof the light-emitting device, it is usually in the range of 0.04μm²-2.25 mm².

Light-Transmissive Electroconductive Member

The light-transmissive electroconductive member 20 (20A, 20B) comprisesa transparent substrate 21 (21A, 21B) having flexibility, and alight-transmissive electroconductive layer 25 (25A, 25B) formed on thesurface of the transparent substrate 21. A pair of thelight-transmissive electroconductive members 20 sandwich the LED chip 10so that the light-transmissive electroconductive layers 25 thereof areelectrically connected to the electrode layers 15 (15A, 15B) of the LEDchip 10. The light-transmissive electroconductive layers 25 each form acircuit pattern for driving at least one LED chip 10 of one or pluraltypes.

More specifically, the light-transmissive electroconductive members 20includes a first light-transmissive electroconductive member 20Acovering the LED chip 10 so that the light-transmissiveelectroconductive layer 25A is electrically connected to the surface ofthe first electrode layer 15A of the LED chip 10, a secondlight-transmissive electroconductive member 20B covering the LED chip 10so that the light-transmissive electroconductive layer 25B iselectrically connected to the surface of the second electrode layer 15Bof the LED chip 10.

Transparent Substrate

The transparent substrate 21 is a substrate which is transparent orcapable of light-transmission and flexible, and may be in a sheet form.The transparent substrate 21 can also be in a form of sheet having acurved surface as long as it retains light-transmissivity andflexibility.

The transparent substrate 21 has a total light transmittance (measuredbased on Japanese Industrial Standards JISK7375:2008) of usually 90% ormore, more preferably 95% or more, so as to provide the light-emittingdevice of the present invention will have a total light transmittance ofusually 1%-80%, preferably 5 to 70%. A higher total light transmittanceprovides a higher luminous intensity of the light-emitting device and isgenerally preferred, but a total light transmittance exceeding 80% maybe undesirable, since the circuit pattern of the light-transmissiveelectroconductive member is liable to be recognized clearly. On theother hand, a total light transmittance lower than 1% is not desirable,since it becomes impossible to recognize each LED as a luminescent spot.

The transparent substrate 21 may have a flexural modulus (measuredaccording to ISO178 (JIS K7171:2008)) of at least 150 kgf/mm²,preferably 200 to 320 kgf/mm². The light-emitting device 1 may beprovided with a preferable degree of flexibility if the transparentsubstrate 21 has a flexural modulus in a range of from 150 kgf/mm² to320 kgf/mm².

The transparent substrate 21, may comprise, e.g. polyethyleneterephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC),polyethylene succinate (PES), “ARTON” (registered trademark) availablefrom JSR Corp., acrylic resin, etc. The transparent substrate 21 mayhave a thickness of, e.g. usually 50-300 μm, preferably 50-200 μm.

Light-Transmissive Electroconductive Layer

Although the material thereof is not particularly limited, thelight-transmissive electroconductive layer 25 may comprise, e.g. a thickfilm comprising a light-transmissive resin binder containing therein aplurality of light-transmissive electroconductive fillers in a mutuallycontacting state; a thin film of an electrical conductor material formedby sputtering or vapor deposition; a mesh electrode comprising anon-light transmissive conductor, such as silver-based fine particles;etc. The light-transmissive electroconductive layer 25 is a layer whichhas electroconductivity as well as light-transmissivity formed on thesurface of the transparent substrate 21. The light-transmissiveelectroconductive layer 25 may have a transmittance of usually 10 to85%.

More specifically, the light-transmissive electroconductive layer 25,may comprise: (1) a conductor film formed by sputtering, vapordeposition, etc., of light-transmissive conductors, such as ITO (indiumtin oxide), ZnO (zinc oxide), etc.; (2) an applied and cured resin filmof a slurry comprising particulates of light-transmissive conductors,such as ITO, ZnO, etc. as mentioned above, disperse in alight-transmissive resin (e.g. ultraviolet-curable acrylic resin); (3)mesh electrodes, formed by patterning through application, exposure anddevelopment of a photosensitive compound, such as silver halide, of anon-light-transmissive conductor such as Ag, patterning through screenprinting of Ag-based or Au-based fine particles, patterning by laserirradiation or photo-etching, etc. of a film of a non-light-transmissiveconductor, such as Ag, Cu, etc., formed by sputtering or electron beamvapor deposition; etc.

Among these, (1) has an advantage that a thin film electrode havingstable conductivity can be formed simply, but is liable to have aninferior adhesion with a contacting light-transmissive elastomer, thusbeing liable to result in an inferior flexural resistance. In contrastthereto, (2) and (3) provide light-emitting devices with good flexuralresistance, and particularly (2) shows especially good performance inthis respect but is accompanied with a difficulty that theelectroconductivity thereof is liable to change after standing for along period at relatively high temperatures (e.g. about 100° C).Although (3) is good in balance of flexural resistance and electricconduction stability, it involves difficulties in troublesome processingand a rather low conductivity level attained. Therefore, it is desirableto effect an appropriate selection from these, depending on the purpose,manner of use, etc. of the light-emitting device obtained.

The thus-obtained light-transmissive electroconductive layer 25 maygenerally have a total light transmittance of 10 to 85% and a sheetresistivity (according to a method described later) of at most 1000ohm/□. Particularly, in view of the respective characteristics of(1)-(3) described above, it is preferred that the conductor film (1) isformed in a thickness of 0.05-2 μm and has a sheet resistivity of 10-500ohm/□, particularly 10-50 ohm/□.

On the other hand, it is preferred that the coating film-typeelectroconductive layer (2) contains particulate conductor-dispersedtherein, such as bar- or plate-shaped light-transmissive particulate(filler) conductors, such as ITO, ZnO, etc., having an average particlesize (measured by laser diffractometry according to ISO13320-1 (JISZ8825-1)) of 10-200 nm, especially 20-100 nm, and an aspect ratio(longer axis diameter/shorter axis or thickness) of at least 2 dispersedin a proportion of at least 50 wt. % and at most 95 wt. % or at most 90wt. %, within a transparent binder of an acrylic resin, etc. and isformed to have a total light transmittance of at least 80%, particularly85-99%, to have a thickness of 0.5-10 μm, particularly 1-5 μm, and asheet resistivity of 10-500 ohm/□, particularly 10-50 ohm/□.

The particulate conductor-dispersed film-type electroconductive layer(2) shows electroconductivity represented by the above-mentioned sheetresistivity because the conductor fine particles (filler) dispersedtherein are present in a mutually contacting state. For this purpose, itis desirable that the light-transmissive electroconductive fillerparticles are contained in the light-transmissive electroconductivelayer at a rate of at least 50 wt. % and at most 95 wt. %.

If the coating-type light-transmissive electroconductive layer 25 has athickness less than 0.5 μm, the layer is liable to have a regioncomprising only a light-transmissive binder having no conductivity sothat the light-transmissive electroconductive layer 25 is liable to havean excessively large sheet resistivity. Moreover, if thelight-transmissive electroconductive layer 25 has a thickness less than0.5 μm, the layer is caused to have a lower strength and inferiordeformation followability, so that the light-transmissiveelectroconductive layer 25 is liable to be broken where the layer isbent at a large degree by being abutted to an angular part such as anedge of the electrode layer 15 of the LED chip 10. On the other hand, ifthe thickness of the light-transmissive electroconductive layer 25exceeds 10 μm, the formation thereof becomes difficult because of toolarge a thickness and the layer is liable to be broken due to bending.

The light-transmissive electroconductive layer 25 has a flexuralresistance and deformation followability because the conductor fineparticles (filler) dispersed therein are mutually bonded with thelight-transmissive resin binder.

On the other hand, the light-transmissive electroconductive layer of themesh-type (3) is preferably formed as a mesh of a non-light-transmissiveconductor, such as Au or Ag, in a line thickness having across-sectional area-equivalent diameter of 2-20 μm and at a spacing of100-1000 μm so as to provide a total light transmittance of 10 to 85%,and a sheet resistivity of 0.1-50 ohm/□, especially 0.1-10 ohm/□.

Au, etc., forming the mesh electrode is a non-light-transmissivematerial, but as the mesh electrode occupies only a small arealpercentage, it provides a mesh electrode which shows the above-mentionedlevel of total light transmittance as a whole.

The light-transmissive electroconductive layer 25 according to any ofthe above-mentioned compositions (1)-(3) may be patterned, by a method,such as laser processing, etching, etc., into an electroconductive layer25A connected to the electrode layer (cathode) 15A on the N-typesemiconductor layer 42, or an electroconductive layer 25B connected tothe electrode layer (anode) 15B on the P-type semiconductor layer 44.

Light-transmissive Elastomer Layer

The light-transmissive elastomer layer 30 comprises an elastomer and isbonded to the circumference 13 of the LED chip 10 and the surfaces ofthe light-transmissive electroconductive layers 25 (25A, 25B) of thelight-transmissive electroconductive member 20 (20A, 20B), therebybinding the LED chip 10 with the light-transmissive electroconductivemembers 20 (20A, 20B).

Thus, in an arrangement that the LED chip 10 is sandwiched between thelight-transmissive electroconductive layer 25A side of thelight-transmissive electroconductive member 20A and thelight-transmissive electroconductive layer 25B side of thelight-transmissive electroconductive member 20B, the light-transmissiveelastomer layer 30 is disposed to fill up a space or region which isformed between the light-transmissive electroconductive member 20A andthe light-transmissive electroconductive member 20B and surrounds theperipheral wall 13 of an LED chip.

More specifically, the light-transmissive elastomer layer 30 also fillsup a gap space or crevice gap 48 formed between concavities 46 of thesurface unevenness 45 of the electrode layer 15 of the LED chip 10 andthe surface 26 of the light-transmissive electroconductive layer 25A ofthe light-transmissive electroconductive member 20A. Thus, if the gapspace 48 is also filled up with the light-transmissive elastomer layer30, the light-transmissive electroconductive layer 25A of thelight-transmissive electroconductive member 20A becomes free fromcracking, and the electrode layer 15 of the LED chip 10 and thelight-transmissive electroconductive layer 25A of the light-transmissiveelectroconductive member 20A are bonded firmly, so that firm electricalconnection arid therefore a lighting state are retained even if thelight-emitting device 1 is subjected to intense bending or applicationof heat cycle.

FIG. 5 shows an example of scanning electron microscope photographshowing a surface of the first electrode layer 15A of Au of the LED chip10 after peeling between the first electrode layer 15A and the firstlight-transmissive electroconductive member 20A.

FIG. 5 shows a state where the light-transmissive elastomer layer 30adheres firmly to the surface of the electrode layer 15A along or evenmore with the surface unevenness of the first electrode layer 15A of theLED chip 10 after the peeling. FIGS. 6A to 6C show surface states of afirst electrode layer 15A of the LED chip 10 after peeling between thefirst electrode layer 15A and a first light-transmissiveelectroconductive member 20A in a light-emitting device according to thefirst embodiment; among which FIG. 6A is a scanning electron microscopephotograph, FIG. 6B is an elemental mapping photograph for carbonaccording to energy dispersion-type X-ray analysis (EDX), and FIG. 6C isan elemental mapping photograph for tin according to EDX.

In view of these figures, it is shown that element tin (originated froman ITO-dispersed electroconductive layer 25A) is hardly observed in aregion where element C (elastomer 30 origin) is frequently observed onthe surface of the first electrode layer 15A of the LED10, while elementC is little observed where much element tin is present. FIGS. 6A-6C areshown at a magnification of 250 times, and have been taken at anelectron beam accelerating voltage of 15.0 kV. Numerals indicated at anupper part of FIG. 6A represent a gray scale of the SEM secondaryelectron image and the gray scale indicated with numerals at upper partsof FIGS. 6B and 6C represent atomic percentages of elements C (carbon)and Sn (tin), respectively, on the observed face. Incidentally, FIGS.6A-6C can be observed as color pictures and the atomic % can berecognized not by a gray scale but as a color change, at the time ofactual measurement.

In FIGS. 6A-6C, the region where much tin is observed with almost no C,represents a region (region a) where the first electrode layer 15A ofthe LED chip 10 and the first light-transmissive electroconductive layer25A (represented by the light-transmissive electroconductive filler ITOcontained therein) contacted directly with each other. Here, the tinobserved in FIG. 6C shows that the light-transmissive electroconductivefiller containing tin in the layer 25A was transferred to the firstelectrode layer 15A at the time of peeling between the first electrodelayer 15A and the first light-transmissive electroconductive layer 25A.These results show that a. good electrical connection was establishedbetween the first electrode layer 15A and the first light-transmissiveelectro-conductive layer 25A of the LED chip 10.

In FIGS. 6A-6C, the region where much carbon is observed with almost notin on the first electrode layer 15A of the LED chip 10, represents aregion (region b) where the light-transmissive elastomer layer 30 entersbetween the first electrode layer 15A of the LED chip 10 and the firstlight-transmissive electroconductive layer 25A to mechanically join thefirst electrode layer 15A and the first light-transmissiveelectroconductive layers 25A of the LED chip 10. Thus, it has been foundbecause of the co-presence of the region a and the region b that, in thelight-emitting device of the present invention, an electrical connectionand mechanical junction are both satisfactorily maintained between thefirst electrode layer 15A and the first light-transmissiveelectroconductive layer 25A of the LED chip 10.

Moreover, although an unevenness finer than unevenness 45 of the surfaceof the electrode layer 15A is usually present on the surface of theelectrode layer 15B of the LED chip 10, the light-transmissive elastomerlayer 30 is formed also in the minute gap space between the minutesurface unevenness of the electrode layer 15B and the surface of thelight-transmissive electro-conductive layer 25B of thelight-transmissive electroconductive member 20B. Furthermore, on theelectrode-layer 15B side, the light-transmissive elastomer existsabundantly near the center of the electrode layer, and, as for anelectrode peripheral part, there is clearly observed a trace that theelectrode and the light-transmissive electroconductive layer toucheddirectly with each other. Thus, if the light-transmissive elastomerlayer 30 is formed also in the minute crevice space on the surface ofthe light-transmissive electroconductive layer 25B and thelight-transmissive elastomer is also present in the other region, thelight-transmissive electroconductive layer 25B of the light-transmissiveelectroconductive member 20B is less liable to be cracked, and theelectrode layer 15 of the LED chip 10 and the light-transmissiveelectroconductive layer 25B of the light-transmissive electroconductivemember 20B are bonded firmly, so that an electrical connection andtherefore a lighting state are firmly kept even under severe bending andapplication of a thermal cycle.

The present inventor peeled the light-transmissive electroconductivemembers apart from the LED chips of the light-emitting devices andmeasured an areal percentage of a region on an LED electrode where acarbon atomic % is at least 50% with respect to the area of the LEDelectrode after the peeling based on planar carbon analysis according tothe EDX observation (hereafter called an “elastomer coverage (on an LEDelectrode)” and a measuring method therefor is described later). As aresult, the present inventor has found that good electrical connectionand mechanical junction are realized when the elastomer coverage is10-90%, preferably 20-80%, both on the LED electrodes 15A and 15B, andalso has found a solution for realizing the condition.

The light-transmissive elastomer layer 30 is a layer of an elastomerhaving a light-transmissivity but no electroconductivity, and has atotal light transmittance of 1 to 99%, preferably 5 to 90%.

The Vicat softening temperature (of which the measuring method ismentioned later) of the elastomer for the light-transmissive elastomerlayer 30 is preferably 80° C. to 160° C., more preferably 100° C. to140° C. Moreover, the tensile storage modulus of the elastomer for thelight-transmissive elastomer layer 30 is in the range of preferably 0.01to 10 GPa, more preferably 0.1 to 7 GPa, respectively between 0 to 100°C.

It is preferred that the elastomer used for the light-transmissiveelastomer layer 30 does not melt at the Vicat softening temperature,arid shows a tensile storage modulus at the Vicat softening temperatureof at least 0.1 MPa, and a melting temperature which is at least 180°C., more preferably 200° C. or more, or is higher than Vicat softeningtemperature by at least 40° C, more preferably by 60° C. or more. Theglass transition temperature of the elastomer used for thelight-transmissive elastomer layer 30 is preferably at most −20° C.,more preferably −40° C. or below.

An elastomer is an elastic polymer material and is a resin. Theelastomer used here is a thermoplastic elastomer as is understood fromthe fact that it has a Vicat softening temperature. It is a polymerwhich shows rubber elasticity, e.g. around room temperature and showsthermoplasticity at higher temperatures. Thermoplastic elastomer can beof a type which is polymerized on temperature increase up to a curingtemperature and has thermoplasticity thereafter. The production processof the light-emitting device according to an embodiment of the presentinvention is characterized in that such a thermoplastic elastomer sheetin a state of being inserted between the LED chip electrode and theelectroconductive layer is subjected to a vacuum press at a temperaturewhich is equivalent to or slightly above the Vicat softening point andbelow the melting temperature, thereby deforming the elastomer sheetwithout causing excessive plasticity or flowing to fill the gaps betweenthe LED chip electrode and the electroconductive layer and improve thebonding (peeling prevention) and electric connection between the LEDchip electrode and the electroconductive layer.

Examples of the elastomer used for the light-transmissive elastomerlayer 30, may include an acrylic elastomer, an olefinic elastomer, astyrene-based elastomer, an ester-based elastomer, a urethane-baseelastomer, etc.

It is possible to contain another resin component, filler, additive,etc., if needed.

In order to improve the filling effect of the elastomer in the productlight-emitting device and to secure a contact between the LED chipelectrode and the electroconductive layers, it is desirable that thethickness of the light-transmissive elastomer layer 30 is equal to orbelow the thickness of the LED chip 10. The light-transmissive elastomerlayer 30 may have an upper limit thickness which is preferably smallerby at least 5 μm, more preferably smaller by at least 10 μm, still morepreferably smaller by at least 20 μm, than the thickness (height) of theLED chip 10. Moreover, the light-transmissive elastomer layer 30 mayhave a lower limit thickness which is usually ½, preferably ⅗, of thethickness of the LED chip 10.

Here, the thickness of the light-transmissive elastomer layer 30 refersto a thickness of the light-transmissive elastomer layer 30 measured ata part which is separated 100 μm or more from the peripheral wall of theLED body 11 of the LED chip 10 and, in a region between the neighboringLEDs, a thickness of the light-transmissive elastomer layer 30 at athinnest part between the LEDs. This thickness usually does not differsubstantially from the total thickness of a pair of elastomer sheetsdisposed over the upper and lower faces of the LED chip before thevacuum pressing.

Production Process

A production process for the light-emitting device 1 (FIG. 1 ) isexplained with reference to FIG. 7 .

For production of a light-emitting device 1,light-transmissive-elastomer sheets 35 are placed between electrodelayers 15 of an LED chip 10 and light-transmissive electroconductivelayers 25 of light-transmissive electroconductive members 20, and apreliminary press is performed at a weak pressure, to firm a temporarylaminate. Then, a working environment is evacuated to a vacuum, in sucha vacuum environment, the temporary laminate is pressure-bonded at atemperature (Tp) which is lower by at most 10° C. and higher by at most30° C., preferably by at most 20° C., than the Vicat softening point(Tv) of the light-transmissive elastomer (i.e., Tv−10° C.≤Tp≤Tv+30° C.,more preferably Tv−10° C.≤Tp≤Tv+20° C.).

In addition, the tensile storage modulus at the Vicat softeningtemperature of the elastomer used for the light-transmissive elastomerlayer 30, is desirably at least 0.1 MPa, more preferably at least 1 MPa,e.g. 1 MPa-1 GPa.

Moreover, the tensile storage modulus at the heat pressure-bondingtemperature of the elastomer used for the light-transmissive elastomerlayer 30, is desirably at least 0.1 MPa, more preferably at least 1 MPa,e.g. 1 MPa-1 GPa.

The desirable ranges for the Vicat softening temperature, the tensilestorage modulus at the hot pressure-bonding temperature and otherparameters described above also hold true with other embodimentsdisclosed herein.

Lamination and Vacuum Hot Pressing

More specifically, with reference to FIG. 7 , alight-transmissive-elastomer sheet 35 of a predetermined thickness isdisposed on a light-transmissive electroconductive layer 25B of alight-transmissive electroconductive member 20B so as to cover theentirety of the light-transmissive electroconductive layer 25B, and oneor more LED chips 10 are arranged at predetermined position and in apredetermined direction on the light-transmissive-elastomer sheet 35 soas to provide a desired display pattern in a resultant light-emittingdevice. Further thereon, a light-transmissive-elastomer sheet 35 of apredetermined thickness is disposed, and thereon, a light-transmissiveelectroconductive member 20A is disposed at a predetermined positionwhile directing its light-transmissive electroconductive layer 25Adownward. The light-transmissive-elastomer sheet has a shape whichcovers the entirety of the light-transmissive electro-conductive layer25A. The above-described order of lamination can be reversed upsidedown.

Next, the resultant laminate is subjected to a preliminary press, andthe working environment is made vacuum. In such a vacuum atmosphere,pressing is performed for a predetermined period of, e.g. 20 to 60minutes while heating the laminate. The heating temperature for thevacuum hot pressing is, e.g. usually 80-180° C., preferably 100-160° C.,The degree of vacuum (absolute pressure) for the vacuum hot pressing is,e.g. usually at most 10 kPa, preferably 5 kPa or less. The pressureapplied for the vacuum hot pressing is, e.g. usually 0.5-20 MPa (5-200kgf/cm²), preferably 0.6-12 MPa (6-120 kgf/cm²)

As a result, the light-transmissive-elastomer sheets 35 in the laminateare softened to envelope the LED chip 10 while preventing the crack orfracture due to pressurization of the light-transmissiveelectroconductive layers, and the softened light-transmissive elastomerlayers are bonded and unified with each other to form alight-transmissive elastomer layer 30. Simultaneously therewith, theelectrodes of the LED chip and the light-transmissive electroconductivelayers mutually contact and take electric connection with each other.Vacuum hot pressing is performed so that the thickness of thelight-transmissive elastomer layer 30 may become smaller than thethickness of the LED chip 10. At the end of the vacuum hot pressing, alight-emitting device 1 as shown in FIG. 1 is obtained.

During the vacuum hot pressing, stress is locally added to thelight-transmissive electroconductive layers 25 of the light-transmissiveelectroconductive members 20 as they contact the electrode layers 15 ofthe LED chip 10. More specifically, a thrust from the convexities 47 ofthe electrode layer 15A of the LED chip 10 is added to thelight-transmissive electroconductive layer 25A of the light-transmissiveelectroconductive member 20A, as shown in FIG. 2 . Moreover, thelight-transmissive electroconductive layer 25B of the light-transmissiveelectroconductive member 20B receives a thrust from convexitiesconstituting the unevenness 45 on the electrode layer 15B of the LEDchip 10 and a thrust from the angle part 18 of the electrode layer 15Bof the LED chip 10.

However, when the elastomer laminate shown in FIG. 7 is pressed in thedirection of arrows P, the crevice space or gap 48 (FIG. 2 .) betweenthe surface of the electrode layer 15 (15A, 15B) of the LED chip 10 andthe light-transmissive electroconductive layer 25 (25A, 25B) of thelight-transmissive electroconductive member 20 (20A, 20B) is filled upwith the light-transmissive elastomer layer 30 formed with the softenedelastomer sheets 35, so that the occurrence of crack and fracture of thelight-transmissive electroconductive layer 25 of the light-transmissiveelectroconductive member 20 possibly caused by the thrusts from theconvexities of the unevenness 45 on the surface of the electrode layer15 (15A, 15B) of the LED chip 10, is suppressed.

Moreover, the light-transmissive electroconductive layer 25 (25A, 25B)of the light-transmissive electroconductive member 20 compriseslight-transmissive-electroconductive-filler particles and alight-transmissive resin binder for bindinglight-transmissive-electroconductive-filler particles while keepingmutual contact between the adjacent particles, and has flexibility orfollowability to deformation. For this reason, even if local thrust isapplied to the light-transmissive electroconductive layer 25 of thelight-transmissive electroconductive member 20 from the convexities 47of the electrode layer 15A of the LED chip 10, or from the angle part 18of the electrode layer 15B, a fatal crack in the light-transmissiveelectroconductive layer 25 is hardly caused and, even if a crack arises,a lighting state can be maintained, since the electric connectionreliability of the light-transmissive electroconductive layer is highowing to the presence of the light-transmissive resin binder. Further,the resultant light-emitting device 1 hardly causes a fatal crack whenit is severely bent and, even if a crack arises, a lighting state can bemaintained, since the light-transmissive resin binder maintains theelectric connection of the light-transmissive electroconductive layer.

The control the above-mentioned elastomer coverage in a desirable rangemay be achieved to some extent by appropriately controlling the totalthickness of the light-transmissive elastomer layers 35 within the rangeof, e.g. 40 to 99%, preferably 60 to 85%, of the thickness (height) ofthe LED chip 10, but in addition thereto, it is desirable to adjust theshape, material and cushioning properties of the press machine surfacecontacting the light-transmissive electroconductive member 20 during thevacuum hot pressing, and the conditions of the vacuum hot pressing, suchas temperature, pressure and timing. The combination of concreteconditions can be suitably chosen depending on the design of alight-emitting device, and the design of vacuum hot pressing apparatus.

The local intrusion or penetration of the light-transmissive elastomerlayer 30 between the electrode layer 15 of the LED chip 10 and thetransparent electroconductive layer 25, may be performed by methodsother than above-mentioned manufacturing process, such as a method ofdisposing granular or pillar-shaped light-transmissive elastomer of asuitable size on the electrode layer 15 of the LED chip 10, followed bya step of vacuum hot pressing; and a method of applying or spraying theemulsion of light-transmissive-elastomer powder on the transparentelectroconductive layer 25 or the electrode layer 15 of the LED chip 10,followed by drying thereof and vacuum hot pressing, and the productionprocess is not limited to the above-mentioned process. However, in viewof the ease of production, the above-mentioned production process isexcellent.

Effect of the Production Process

According to the production process, the light-emitting device 1 iseasily producible. Moreover, since the LED chip 10 is sandwiched by thelight-transmissive elastomer layers 35, the LED chip 10 can be reliablyfixed for the production.

Function

The function of the light-emitting device 1 is explained.

In the light-emitting device 1, the light-transmissive elastomer layer30 is formed also in the crevice space 48 between the concavities 46 ofthe unevenness 45 on the surface of the electrode layer 15 (15A, 15B) ofthe LED chip 10, and the surface 26 of the light-transmissiveelectroconductive layer 25 (25A, 25B) of the light-transmissiveelectroconductive member 20 (20A, 20B), so that the light-transmissiveelectroconductive layer 25 (25A, 25B) hardly causes a crack or afracture, even if the convexities 47 of the unevenness 45 on the surfaceof the electrode layer 15 (15A, 15B) of the LED chip 10 abut onto thesurface 26 of the light-transmissive electroconductive layer 25 (25A,25B) of the light-transmissive electroconductive member 20 (20A, 20B).As a result, the electric connection reliability of thelight-transmissive electroconductive layer becomes high, so that alighting state can be maintained, even if the light-emitting device 1 isbent severely or subjected to a thermal cycle.

Moreover, in the light-emitting device 1, the light-transmissiveelastomer layer 30 is formed also in the crevice space 48 between theconcavities 46 of the unevenness 45 on the surface of the electrodelayer 15 (15A, 15B) of the LED chip 10, and the surface 26 of thelight-transmissive electroconductive layer 25 (25A, 25B) of thelight-transmissive electroconductive member 20 (20A, 20B), so that apositional deviation is hardly caused in the direction of extension ofthe boundary between the electrode layer 15 of the LED chip 10, and thelight-transmissive electroconductive layer 25 of the light-transmissiveelectroconductive member 20. For this reason, the electric reliabilityof the light-emitting device 1 is high.

Furthermore, since the light-transmissive electroconductive layer 25 ofthe light-emitting device 1 is formed by binding a multiplicity oflight-transmissive electroconductive fillers with a light-transmissiveresin binder, the light-transmissive electroconductive layer 25, as awhole, shows a flexural resistance or followability to deformation.Thus, even when the light-transmissive electroconductive layer 25 isbent along with an edgy part, such as an angle portion of the electrodelayer 15, the light-transmissive resin binder portion binding alight-transmissive electroconductive filler bends or deforms, so thatthe light-transmissive electroconductive layer 25 is rich infollowability to such an edgy part like an angle portion of theelectrode layer 15. For this reason, when the light-transmissiveelectroconductive layer 25 is severely bent along with an edgy part,such as an angle part of the electrode layer 15, e.g. during productionof the light-emitting device 1, a fatal crack hardly occurs in thelight-transmissive electroconductive layer 25 so that lighting abilityis maintained by retaining electric connection of the light-transmissiveelectroconductive layer with the light-transmissive resin binder.Incidentally, although the unevenness 45 is shown only on the electrodelayer 15A of the LED chip 10 in FIG. 2 , similar unevenness is actuallypresent also on the electrode layer 15B.

Comparative Manufacturing Processes

The production process according to this embodiment is characterized bythe features that (1) for providing an electric connection between theLED electrode layer 15 and the light-transmissive electroconductivelayer 25, an elastomer sheet 35 that does not melt or have a lowviscosity (meant herein to assume a tensile storage modulus less than0.1 MPa) during the vacuum hot pressing step is inserted between the LEDelectrode 15 and the light-transmissive electroconductive layer 25, and(2) the laminate including the light-transmissive electroconductivemember 20, the elastomer sheet 35 and the LED chip 10, is subjected tovacuum hot pressing.

A Manufacturing Process Wherein Vacuum Hot Pressing is Performed WithoutInserting an Elastomer Between an LED Electrode and a Light-TransmissiveElectroconductive Member

An example of production not satisfying the feature (1) performed by thepresent inventor is explained.

FIG. 8 illustrates Production example 1 for a light-emitting devicewhich was performed by forming a laminate consisting oflight-transmissive electroconductive members 20, an elastomer sheet 35and an LED chip 10 without inserting a light-transmissive-elastomersheet 35 between the electrode layer 15A of the LED chip, and thelight-transmissive electroconductive layer 25A, and subjecting theresultant laminate to vacuum hot pressing, otherwise in a similar manneras in the above-mentioned first embodiment for production of thelight-emitting device 1.

FIG. 9 illustrates Production example 2 for a light-emitting devicewhich was performed by forming a laminate consisting oflight-transmissive electroconductive members 20, an elastomer sheet 35and the LED chip 10 without inserting a light-transmissive-elastomersheet 35 between the electrode layer 15B of an LED chip, and thelight-transmissive electroconductive layer 25B, and subjecting theresultant laminate to vacuum hot pressing, otherwise in a similar manneras in the above-mentioned first embodiment for production of thelight-emitting device 1.

A light-emitting device 90 produced by Production example 1 and alight-emitting device 90A produced by Production example 2 are explainedbelow.

FIG. 10 is a partial enlarged view of a section of the light-emittingdevice 90 produced by Production example 1. FIG. 11 is a partialenlarged view of section B1 in FIG. 10 . FIG. 12 shows an example ofcross-sectional photograph of the light-emitting device 90 of thelight-emitting device 90 produced by Production example 1. FIG. 13 showsan example of cross-sectional photograph of the light-emitting device90A produced by Production example 2.

Luminescent Device 90 of Production Example 1

As shown in FIG. 10 -FIG. 12 , in the light-emitting device 90 obtainedby Production example 1, the crevice gap 48 formed between the concavity46 of the unevenness 45 of the surface of the electrode layer 15 of theLED chip 10 and the surface 26 of the light-transmissiveelectroconductive layer 25A of the light-transmissive electroconductivemember 20A serves as a vacant gap 91, and the light-transmissiveelastomer 30 is hardly present there. Thus, the elastomer coverage wasclearly below 10%.

As a result of a bending resistance test and a thermal cycling test, thelight-emitting device 90 readily caused a lighting failure. As shown inFIG. 11 , a crack 92 was caused at a part, of the light-transmissiveelectroconductive layer 25A of the light-transmissive electroconductivemember 20A, abutting the convexity 47 of the electrode layer 15A of theLED chip 10. This is presumably because the stress from the convexity 47concentrated under severe bending, leading to the lighting failure underapplication of bending and thermal cycles.

Second Light-Emitting Device 90A of Production Example 2

FIG. 13 is a scanning electron microscope photograph of a section of alaminate after vacuum hot pressing of the laminate consisting of thelight-transmissive electroconductive member 20, the elastomer sheet 35and the LED chip 10 without inserting the light-transmissive elastomersheet 35 between the electrode layer 15B of an LED chip and thelight-transmissive electroconductive layer 25B.

As shown in FIG. 13 , in the light-emitting device 90A, there occurred avacant gap 91 around the electrode layer 15B of the LED chip 10, wherealmost no light-transmissive elastomer layer 30 was present in thevacant gap 91. Thus, the elastomer coverage was clearly below 10%.

For this reason, as a result of the bending resistance test and thermalcycling test, the light-emitting device 90A readily caused a lightingfailure. This is presumably because a crack occurred at a part, of thelight-transmissive electroconductive layer 25B of the light-transmissiveelectroconductive member 20B, abutting the angle part of the electrodelayer 15B of the LED chip 10, and the stress from the angle partconcentrated under severe bending.

Luminescent Device According to a Production Process of Patent Document5

JP-A 2012-84855 (Patent document 5) discloses a process for producing alight-emitting device, comprising: forming a through-hole in anintermediate layer comprising an acrylic elastomer, disposing alight-emitting element in the through-hole, and sandwiching the frontand back faces of the light-emitting element with a pair of supports.

More specifically, there is disclosed a process, wherein an acrylicelastomer sheet having a through-hole therein is placed in contact on afirst support, a light-emitting element is disposed in the through-hole,a second support is disposed in contact on the acrylic elastomer sheet,and the resultant laminate is sandwiched and press-heated with a heatingdrum to produce a light-emitting device.

In the light-emitting device manufactured by this process, a vacant gap91 occurred around the electrode layer 15 of the LED chip 10, and almostno light-transmissive elastomer layer 30 was present in the vacant gap91, so that the elastomer coverage was clearly below 10%. Moreover, manyair bubbles remained near the LED chip.

In the light-emitting device according to the production process ofPatent document 5, although the lighting was generally realized in theinitial state, lighting failure was caused as the time passed in manycases. Moreover, lighting failure was readily caused during the bendingtest and the thermal cycling test.

Luminescent Device C According to a Production Process of PatentDocument 3

Patent document 3 discloses a process wherein a hot melt adhesive,instead of the light-transmissive elastomer sheet 35, is disposedbetween the electrode layer 15 of an LED chip and the light-transmissiveelectroconductive layer 25, and the resultant laminate consisting of thelight-transmissive electroconductive member 20, the elastomer sheet 35and the LED chip 10 is subjected to hot pressing (while melting the hotmelt adhesives). The light-transmissive elastomer used in the productionprocess of the present invention is a material which needs to maintainthe nature of a light-transmissive elastomer in a vacuum hot pressingstep, and is a quite different material from a hot melt adhesive whichis a material that melts at a processing temperature and is inapplicableto vacuum hot pressing.

As a result, the light-emitting device C according to Patent document 3was difficult to manufacture without leaving air hubbies in thelight-emitting device including a region between the electrode layer 15of the LED chip and the light-transmissive electroconductive layer 25,so that a vacant gap not filled with the hot melt adhesive remainedbetween the electrode layer 15 of an LED chip, and thelight-transmissive electroconductive layer 25, and also a crack occurredat a part where the light-transmissive electroconductive layer 25abutted the electrode layer 15 presumably during the pressing. For thisreason, in the light-emitting device 90C, lighting failure readilyoccurred during the bending test or thermal cycling test.

Second Embodiment

FIG. 14 is a sectional view of a light-emitting device of a secondembodiment. Compared with the light-emitting device 1 shown in FIG. 1 asa first embodiment, the light-emitting device 1A is different in that itincludes an LED chip 10A having two types of electrodes 15A and 15B onone face thereof in place of the LED chip 10, a transparent substrate21D having no light-transmissive electroconductive layer 25 in place ofthe first light-transmissive electroconductive member 20A, and alight-transmissive electroconductive member 20C having two types oflight-transmissive electroconductive layers 25A and 25B in place of thesecond light-transmissive electroconductive member 20B, and the otherstructure is identical to the light-emitting device 1. Accordingly, withrespect to the light-emitting device 1A shown in FIG. 14 as a secondembodiment, the same components as those in the light-emitting device 1shown in FIG. 1 as a first embodiment are denoted by identical symbolsor numerals, and further explanations of structure and function areomitted or simplified.

More specifically, the light-emitting device 1A includes: an LED chip10A having a first and a second electrode layer 15 (15A, 15B) on oneface of an LED body 11A; a light-transmissive electroconductive member20C which includes a transparent substrate 21C and a first and a secondlight-transmissive electroconductive layer 25 (25A, 25B) formed on thetransparent substrate 21C and covers the face having the electrodelayers 15 of the LED chip 10A; a transparent substrate 21D covering theother face of the LED chip 10A; and a light-transmissive elastomer layer30 which consists of an elastomer and is bonded to the circumference 13of the LED chip 10A, the surface of the light-transmissiveelectroconductive member 20C, and the surface of the transparentsubstrate 21D.

In short, the fight-emitting device 1A is formed by sandwiching the LEDchip 10A with the light-transmissive electroconductive member 20C andthe transparent substrate 21D, and bonding the LED chip 10A, thelight-transmissive electroconductive member 20C and the transparentsubstrate 21D with the light-transmissive elastomer layer 30.

LED Chip

FIG. 15 is an enlarged view of the LED chip 10A shown in FIG. 14 .

The LED chip 10A includes the electrode layer 15A as a first electrodelayer and the electrode layer 15B as a second electrode layer formed onone face of the LED body 11A.

Compared with the LED chip 10 used in the light-emitting device 1 as thefirst embodiment, the LED chip 10A differs in that the electrode layer15A and the electrode layer 15B are formed on one face of the LED body11A, and the other composition is the same as the latter. Hereinbelow,only the differences between the LED chip 10A and the LED chip 10 areexplained.

The LED body 11A has an N-type semiconductor layer 42 and a P-typesemiconductor layer 44 on a substrate 41A made of, e.g. semiconductor orsapphire, a luminescence layer 43 is formed between the N-typesemiconductor layer 42 and the P-type semiconductor layer 44.

A face on which the electrode layers 15A (cathode) and 15B (anode) areformed among the faces 71 of the LED body 11A is called a third face 71Cof the LED body 11A. In this example, the third face 71C of the LED body11 is the surface of the P-type semiconductor layer 44. The electrodelayer 15B is formed on the third face 71C.

Moreover, a face opposite to the third face 71C of the LED body 11A andhaving no electrode layer 15A or 15B thereon is called a fourth face 71Dof the LED body 11. The fourth face 71D is a surface of the LEDsubstrate 41A. It is possible to dispose a reflective film (not shown)on the surface of the LED substrate 41A, or on the face 71C. It is alsopossible that the face 71C or the face 71D forms a luminescence face ofLED chip 10. In case where the LED substrate 41A is transparent, almostall the faces of the LED chip 10A can be a luminescence face. Light canbe taken out from either one face or both faces, and a face close to theluminescence layer 43 is hereafter called a luminescence face herein forconvenience.

The electrode layer 15A (cathode), in this example, is formed on andelectrically connected to a non-covered and exposed face 72 of theN-type semiconductor layer 42 which is generally covered with theluminescence layer 43 and the P-type semiconductor layer 44. Since theexposed face 72 of the N-type semiconductor layer 42 and the third face71C of the LED body 11A are disposed in an identical direction as viewedfrom the center of the LED body 11A, the electrode layer 15A is formedon the luminescence layer-side interface 72 of the N-type semiconductorlayer 42 and also disposed on the third face 71 C of the LED body 11A.

The electrode layer 15A and the electrode layer 15B may have a thickness(height) of usually 0.1-10 μm, preferably 1-5 μm, and their thicknessesare almost identical but can differ by about 1 μm at the maximum. Theelectrode layer 15A and the electrode layer 15B are usually formed in atotal area which is smaller than that of the face 71C of the LED body 11so that luminescence may not be obstructed.

A certain degree of unevenness is formed in the exposed face 72 of theN-type semiconductor layer 42 on which the electrode layer 15A isformed. Accordingly, a similar form of unevenness as the unevenness onthe face 72 is formed in the surface of the electrode layer 15A formedon the exposed face 72.

The unevenness of the surface of the electrode layer 15A and theelectrode layer 15B may respectively give a roughness of preferably atleast 0.1 μm. As a result, the surfaces of the electrode layers 15A and15B may have a higher adhesiveness with the light-transmissiveelectroconductive member 20C in the light-emitting device of the presentinvention.

Transparent Substrate

The transparent substrate 21D is identical to the transparent substrate21A constituting the light-transmissive electroconductive member 20A inthe first embodiment, so that explanation thereof is omitted.

Light-Transmissive Electroconductive Member

The light-transmissive electroconductive member 20C includes atransparent substrate 21C having a flexural resistance, and two types oflight-transmissive electroconductive layers 25A and 25B formed on onesurface of the transparent substrate 21C. The light-transmissiveelectroconductive layer 25A is formed so as to be electrically connectedto the electrode layer 15A of the LED chip 10A, and thelight-transmissive electroconductive layer 25B is formed so as to beelectrically connected to the electrode layer 15B of the LED chip 10A.

Compared with the light-transmissive electroconductive member 20B usedin the light-emitting device 1 as the first embodiment, thelight-transmissive electroconductive member 20C differs in that thelight-transmissive electroconductive layer 25A and thelight-transmissive electroconductive layer 25B are formed on one surfaceof the transparent substrate 21C, and the other composition isidentical.

The light-transmissive electroconductive layer 25 formed on thelight-transmissive electroconductive member 20C, similarly as thelight-transmissive electroconductive layer 25 in the first embodiment,may be any form of (1) a conductor thin film, (2) a resin filmcontaining fine particles of light-transmissive conductor dispersedtherein, and (3) a mesh electrode. The light-transmissiveelectroconductive layer 25 formed on the transparent substrate 21C in aform of (1)-(3) above, may be patterned into the electroconductive layer25A connected to the electrode layer (cathode) 15A on the N-typesemiconductor layer 42, or the electroconductive layer 25B connected tothe electrode layer (anode) 15B on the P-type semiconductor layer 44, bylaser processing, etching processing, etc.

The electrode layers 15A and 15B of the LED chip 10A are formed asso-called “pad electrodes” of a metal conductor, such as Au, and theyare electrically connected to the light-transmissive electroconductivelayers 25A and 25B, respectively, after positional alignment and vacuumpressing. When the thus-obtained light-emitting device was subjected torepetitive bending, the occurrence of lighting failure was observed. Asa result of study thereafter, it was found that the failure was causedwhen the device in a state as shown in FIG. 14 was bent convex upwardsto cause the touching of a front end of the light-transmissiveelectroconductive layer 25A connected to the electrode layer 15A(cathode) with the electrode 15B (anode), thus causing a cathode-anodeshort-circuit. Moreover, according to a farther study, thisinconvenience could be avoided by locally forming a bump electrode of agood conductor, such as Au or Ag, of about 50-100 μm in both diameterand height on each of the pad electrodes 15A and 15B of the LED chip10A, and connecting the bump electrodes to the light-transmissiveelectroconductive layers 25A and 25B, respectively. The short circuitprevention effect by formation of such a bump electrode on a padelectrode can be also attained in the first embodiment of using an LEDchip having electrodes on both faces thereof by forming such a bumpelectrode on a pad electrode having a smaller area than LED chip (theanode electrode 15B in the example of FIG. 1 ).

FIGS. 17 and 18 are schematic cross sectional views of light-emittingdevices 1AA and 1BA which may be prepared by forming such bumpelectrodes 36A and 36B, and a bump electrode 36, in the light-emittingdevices of FIG. 14 and FIG. 1 , respectively. Such a bump electrode 36A,36B or 36 may be formed as follows.

A tip of, e.g. Au wire, is discharged by using a wirebonding apparatusto form an Au bump 365 on a pad electrode 15 (15A, 15B) of an LED chip,e.g. as shown in FIG. 19 , the Au bump 36 is preferably pressed toflatten the top A, and then over the LED chip, the above-mentionedlight-transmissive electroconductive member 20 (20A, 20B) having theelastomer layer 30 and the electroconductive layer 25 (25A, 25B) formedthereon is superposed in positional alignment with the LED chip,followed by vacuum hot pressing, to provide a light-emitting devicehaving introduced the bump electrodes 36A and 36B (or 36).

With respect to the light-emitting device shown in FIG. 17 for example,the bump electrodes 36A and 36B, thus introduced, are arranged inrelative positions with the pad electrodes 15A and 15B and theelectroconductive layers 25A arid 25B, e.g. as shown in a plan view ofFIG. 20 .

Production Process

With reference to FIG. 16 , the production process of the light-emittingdevice 1A is explained.

The light-emitting device 1A having a partial sectional structureschematically shown in FIG. 14 , like the light-emitting device 1 shownin FIG. 1 as the first embodiment, is formed through a process ofdisposing the light-transmissive elastomer sheet 35 between theelectrode layer 15 of the LED chip 10A and the light-transmissiveelectroconductive layer 25 of the light-transmissive electroconductivemember 20; and subjecting the resultant laminate to vacuum hot pressingat a temperature in a range between 10° C. below and 30° C. higher thanthe Vicat softening temperature of the light-transmissive elastomer,thereby joining the LED chip 10A, the light-transmissiveelectroconductive member 20 and the light-transmissive and insulatingsubstrate 21D, with the above-mentioned light-transmissive elastomer.

As different from the first embodiment, it is sufficient to dispose thelight-transmissive elastomer sheet 35 at least between thelight-transmissive electroconductive layers 25C and the electrode faceof the LED chip and it is not necessary to always insert alight-transmissive elastomer sheet between the transparent substrate 21Dand the LED chip. Accordingly, further explanation of a productionprocess is omitted.

According to the scanning electron microscope photograph, the elementalmapping photograph of C by EDX and the elemental mapping photograph oftin by EDC of the surfaces of the electrode layer 15A and 15B afterpeeling at the boundary between the electrode layers 15A and 15B of theLED chip 10, and the light-transmissive electroconductive members 20C,the surfaces exhibited almost identical states as the surface of theelectrode layer 15B in the first embodiment. Especially, both surfacesof the electrode layers 15A and 15B of the LED 10 after peeling betweenthe electrode layers 15A and 15B and the light-transmissiveelectroconductive member 20C, exhibited much C element and almost no tinelement near the surface centers thereof, and conversely, much tinelement and almost no C element near the edges of the electrode layers15 of the LED10.

These results show that the electrode layer 15 and thelight-transmissive electroconductive layer 25 of the LED chip 10A werein a good electrical connection.

Moreover, by existence of the region where a lot of C was present withalmost no tin on the surface of the electrode layer 15 of the LED10, itwas shown that there was a region where the light-transmissive elastomerlayer 30 entered between the electrode layer 15 of the LED chip 10 andthe light-transmissive electroconductive layer 25 to mechanically jointhe electrode layer 15 of the LED chip 10 and the light-transmissiveelectroconductive layers 25. Thus, it was understood that goodelectrical connection and mechanical junction were satisfactorilymaintained between the electrode layer 15 of the LED chip 10A and thelight-transmissive electroconductive layer 25, also in thelight-emitting device of the second embodiment of the present invention.

Also in the second embodiment of the light-emitting device of thepresent invention, good electric connection and mechanical junction arerealized between the electrode layer 15 of the LED chip 10, and thelight-transmissive electroconductive member 20 in case where theelastomer coverage of the LED electrode 15A and the LED electrode 15Bis, 10% to 90%, more preferably 20% to 80%.

In the second embodiment of the present invention, the production isperformed by using an LED 10A on only one face of which the electrodelayers 15 (15A, 15B) are formed, the positional alignment between theelectrode layers 15 of the LED chip 10A and the light-transmissiveelectroconductive layers 25 of the light-transmissive electroconductivemember 20C is required only one side thereof. For this reason,production is easy and the yield of the light-emitting device 1 becomeshigh.

By the way, although the above-mentioned embodiments have beenillustrated and explained mainly with respect to devices containing oneLED chip 10. However, the light-emitting device of the present inventionmay include a plurality of LED chips 10, and it is rather usual thatmore than two LED chips 10 are included and arranged according to adesired display pattern.

Moreover, the light-emitting device can include one or more types ofsemiconductor devices chosen from resistances, diodes, transistors andICs in addition to the LED chip(s) 10, on the surface(s) of thelight-transmissive electroconductive layer(s) 25 of thelight-transmissive electroconductive member(s) 20.

Comparison Between the Light-Emitting Device of the Present Inventionand the Conventional Light-Emitting Device

When the conventional light-emitting device was reexamined during acourse of study up to completion of the present invention, the followingfact has become clear.

More specifically, it has been found that an edge of an electrode on thesurface of a light-emitting element is usually formed so as to providean almost right angle between its surface opposite to thelight-transmissive electroconductive layer of a light-transmissiveelectroconductive member and its side wall, so that at the time ofbending of a light-emitting device or application of a thermal cycle toa light-emitting device, the light-transmissive electroconductive layerof the light-transmissive electroconductive member is pressed andabutted against the edge of the electrode of the surface of thelight-emitting element, thus being liable to produce a crack and abreakage. When the crack or breakage occurs in the light-transmissiveelectroconductive layer, electric connection of a light-transmissiveelectroconductive layer becomes insufficient, and a light-emittingdevice causes a lighting failure. This problem occurs not only inproduction but also in use accompanied with bending or application ofthermal cycle to the light-emitting device. Incidentally, the abutmentof the light-transmissive electroconductive layer at the time ofapplication of thermal cycle to a light-emitting device is caused by adifference in coefficient of thermal expansion between componentmaterials.

Moreover, a commercially available two-face electrode-type LED isusually provided with an unevenness on the substrate face andaccordingly on the surface of the electrode so as to improve theadhesiveness with an electric conduction paste in expectation that theelectrode on the non-light-emitting face is joined to a lead frame withthe electric conduction paste. Moreover, an electrode surface on aluminescence face may be provided with fine unevenness for preventingtotal reflection etc. In such a case, if the light-transmissiveelectroconductive layer of the light-transmissive electroconductivemember is abutted to convexities of such unevenness at the time ofbending and application of thermal cycle to the light-emitting device, acrack or breakage is liable to occur in the light-transmissiveelectroconductive layer. When the crack or breakage occurs in thelight-transmissive electroconductive layer, electric connection of alight-transmissive electroconductive layer becomes insufficient, and alight-emitting device causes a lighting failure.

Furthermore, in the light-emitting device disclosed in Patent document5, the thickness of an intermediate layer is smaller than the thicknessof a light-emitting element. As a result, the light-transmissiveelectroconductive layer of the light-transmissive electroconductivemember is abutted strongly against the surface edges of the electrode ofthe light-emitting element at the time of bending of or application ofthermal cycle to the light-emitting device and is liable to cause crackor breakage at the abutted parts. If the crack or breakage occurs in thelight-transmissive electroconductive layer, electric connection of thelight-transmissive electroconductive layer becomes insufficient, and thelight-emitting device causes a lighting failure.

Thus, it was found that the conventional light-emitting devices involveda problem that the light-transmissive electroconductive layer of alight-transmissive electroconductive member was liable to cause a crackor breakage at the time of bending and application of thermal cycle andduring production. If the crack or breakage occurs in thelight-transmissive electroconductive layer, electric connection of alight-transmissive electroconductive layer becomes insufficient, and alight-emitting device causes a lighting failure.

Moreover, for production of conventional light-emitting devices, thermalcompression bonding has been performed under atmospheric pressure, sothat air bubbles (at a pressure higher than atmospheric pressure) areliable to remain especially around the LED chip in the light-emittingdevice. For this reason, it has been found that the bubbles swell afterthe thermal compression bonding to cause poor electric connection andundesirable appearance due to irregular light scattering, etc. due toair bubbles and swelling.

In the light-emitting device disclosed in Patent documents 4 and 5,since the light-transmissive electroconductive layer and the LEDelectrode are merely physically in contact with each other and with nomaterial having a bonding function therebetween, it has been foundimpossible to maintain a contact between the light-transmissiveelectroconductive layer and the LED, when the light-emitting device isbent in curvature radius of less than about 100 mm, and a lightingfailure occurs in less than several hundreds of thermal cycles betweenhigh and low temperatures.

In the process disclosed in Patent document 3 of performing heat-pressbonding of a light-emitting element electrode and a light-transmissiveelectroconductive layer, after inserting therebetween an electricallyinsulating adhesive, such as a flexible hot melt adhesion sheet, the hotmelt adhesive is heat-melted to be fluidized, intimately contacts theelectrodes and the electroconductive layer and solidifies on cooling toexhibit the bonding ability, whereby electric and mechanical contactsbetween the light-emitting element electrode and the light-transmissiveelectroconductive layer, can be attained. The hot melt adhesive is,however, melted and pressed for welding, as is clearly described inPatent document 3. As a result, under application of a pressure duringproduction, the light-transmissive electroconductive layer of alight-transmissive electroconductive member is abutted against the edgeof an electrode, the surface unevenness of the electrode and a stepwisedifference between the substrate of a light-emitting element and theedge of an active layer, etc., so that the light-transmissiveelectroconductive layer is liable to cause a crack or a breakage whichis however not prevented by a hot melt adhesive as described above.Accordingly, it becomes impossible to maintain a lighting state when itis subjected to a thermal cycling test in temperature range of, e.g. −20to 60° C., or −40° C. to 85° C. usually required of electric parts, orwhen it is severely bent. In the case of bonding an electrode and anelectric conduction circuit layer of an LED chip with an electricallyconductive adhesive, it is very difficult to achieve a sufficientinsulation between a plurality of LED chips carried and, in order tosolve this, there arises a manufacturing cost increase due tocomplication of a connection step and an increase of involved steps,etc. Moreover, when a conductive adhesive is used, it is difficult toensure a flexural resistance of the light-emitting device. Furthermore,it has been found that since a hot melt adhesive is melted on heating,it is difficult to perform an adhesion step under vacuum, and therearises a vacant gap (air bubbles) with the residual air in thelight-emitting device, to result in poor connection and appearance.

Based on the above-mentioned knowledge, the present invention has beencompleted in order to solve the problems of the conventional technology.

Apparatus Including the Light-Emitting Device

The apparatus of the present invention is equipped with theabove-mentioned light-emitting device of the present invention.

Examples of such apparatus suitably equipped with the above-mentionedlight-emitting device of the present invention, may include: electronicappliances, such as a television set and a personal computer; electronicdisplay apparatus, such as an exhibition plate and a bulletin board;movable bodies, such as vehicles, a vessel and an airplane, equippedwith illumination apparatus or display apparatus including alight-emitting device; a building, works, etc. equipped withillumination apparatus or display apparatus including a light-emittingdevice.

EXAMPLES

Examples are shown below, whereas the present invention should not beconstrued as being restricted thereto. Characteristic values andevaluation thereof described in the present specification including thefollowing description are based on methods and standards describedbelow.

Electrode Surface Roughness Ra

Ra value was measured as an arithmetic average roughness value measuredaccording to JIS B 0601-2001 with respect to a region of ⅓ or more ofthe crossing length of an objective electrode.

Sheet Resistivity of a Light-Transmissive Electroconductive Layer

Measured by the 4 terminal method based on JIS K 7194 for any of thethin film-type electroconductive layer, the electroconductivepowder-dispersed resinous electroconductive layer and the meshelectrode.

Elastomer Properties

The following properties were measured for the sheet-form samples to beused.

-   -   Vicat softening temperature was measured according to the A50        method of the JIS K7206 (ISO 306) by using a heat distortion        tester No.148-HD-PC (available from Yasuda Seiki Seisakusho        Ltd.) under the conditions of a test load of 10N and a heating        rate of 50° C./hour.    -   Glass transition temperature and Melting temperature were        measured by performing heat flux differential scanning        calorimetry according to JIS K2121 (ISO 3146), using Shimadzu        differential scanning calorimeter DSC-60 at a heating rate of 5°        C./minute from −100° C. to the heat-absorption peak (melting        point).    -   Tensile storage modulus was measured according to JIS K7244-4        (ISO 6721-4) using an automatic dynamic viscoelasticity meter        (“DDV-01GP”, available from A&D Co., Ltd.) under the conditions        of a constant temperature increase rate of 1° C./minute and a        frequency of 10 Hz. Measurement was performed at 0° C., 100° C.        and the Vicat softening temperature.

Characteristic Evaluation of Product Light-Emitting Device (LED Device)

The following items were evaluated.

Thickness Between the LED Chips of a Light-Transmissive InsulatingElastomer Layer

A thickness of a light-transmissive insulating elastomer layer (in astrip-shaped LED device sample with a length of about 90 mm (width:about 50 mm) including 6 LED chips (each having a planar size of 0.3mm×0.3 mm and a height of 175 μm) arranged in a straight line with aspacing of about 5 mm from each other and connected in series preparedin, e.g. Examples and Comparative Examples described hereafter) in aroom at 20° C., was optically measured at a position 1500 μm separatedfrom an end of an LED chip disposed near the center. An arithmeticaverage of the measured values for 12 sample devices was taken.

Flexural Resistance

Flexural resistance test was performed with respect to six of twelveobtained samples of LED devices under a temperature of 20±2° C., arelative humidity of 60 to 70%, and an environment of normal pressure(86-106 kPa).

First, there were provided plural species of cylinders for measurementhaving radius of 100 mm to 20 mm successively decreasing at a decrementof 10 mm and respectively having a section of a uniform diameter and ofa perfect circle.

Next, each strip-shaped LED device was set so that its longitudinaldirection formed a right angle with the axis of a measurement cylinder,and so that the back (opposite to the light-emitting face) of an LEDchip was disposed along the surface of the measurement cylinder. Then,each LED device was turned on and, in this state, bent at 180 degreesover the surface of the measurement cylinder, to evaluate the lightingstate was maintained. This evaluation was performed sequentially from ameasurement cylinder with a larger radius to a measurement cylinder witha smaller radius, to record two smallest flexural radiuses including 20mm (which is evaluated to represent a practically excellent flexuralresistance) or alternative smallest radiuses and the number of sampledevices having maintained their lighting states at the radiuses.

Thermal Cycling Test

The other six obtained LED device samples was subjected to a thermalcycling test according to JIS C60068-14.

More specifically, each strip-shaped LED device disposed in a horizontalstate and in a lighting state was subjected to a thermal cycling test ina temperature range of −20° C. to 60° C. including 30 minutes each ofstanding at −20° C. and 60° C. and intermediate temperature increase andtemperature decrease respectively at a rate of 3° C./min. (i.e. 1 cycleof 53.3 minutes), and the number of samples in six samples havingmaintained the lighting state was recorded, respectively after 2000cycles, 2500 cycles and 3000 cycles.

Lighting Conditions

As for the lighting conditions for the LED device in the above-mentionedflexural resistance and thermal cycling tests, a predetermineddirect-current voltage was continuously impressed between both endterminals of each LED device so that a basically fixed current of 6 mAwas flowed through 6 LED chips connected in series, and electricitysupply conditions were changed as follows.

-   -   ITO-dispersed resin film:        -   1 μm in thickness: Terminal voltage 25V,        -   3 μm in thickness: Terminal voltage 20V,    -   ITO-sputtered film: Terminal voltage 30V,    -   Ag grain mesh electrode film: Terminal voltage 20V.

Appearance and Sectional Observation

Sampled devices after the preparation were left standing for 24 hours inan environment of temperature of 20±2° C., relative humidity of 60 to70% and normal pressure (86-106 kPa).

Observation of Appearance

Visual examination by viewing with eyes was conducted with respect tolight-transmissive LED light-emitting devices before and after theabove-mentioned flexural resistance test and thermal cycling test.

More specifically, the front and back surfaces of eachlight-transmissive LED device was observed with eyes, and the presenceor absence of air bubbles was checked as a primary check. Samples withwhich no bubbles were observed were judged as “no bubbles” and theexamination was terminated.

On the other hand, samples with which air bubbles were observed by theprimary check were subjected to photographing of air bubbles using amicroscope with a camera (magnification; ×50). Using the photographs, amaximum distance between arbitrarily selected two points on the contourof an air bubble was measured and determined as an outer diameter of thebubble. Whether the thus-determined diameter of bubble was equal to orexceeded the LED chip size or 500 μm, was checked. Based on the aboveexamination, the evaluation was performed according to the followingstandard.

A: Air bubbles were not recognized by the primary check by viewing witheyes.

B: Although air bubbles were slightly recognized by viewing with eyes,no air bubbles having an outer diameter equal to or exceeding the LEDchip size or 500 μm was observed by checking with a microphotograph.

C: The air bubbles were recognized by viewing with eyes and exhibited anouter diameter equal to or exceeding the LED chip size or 500 μm bychecking with a microphotograph.

Sectional Observation

Sectional observation was performed with respect to light-transmissiveLED devices before and after the above-mentioned flexural resistancetest and thermal cycling test. More specifically, eachlight-transmissive stripe-shaped LED device was embedded within a resinfor sectional observation, and the resultant sample was subjected to ionmilling by an ion milling apparatus (“E-3500”, available from HitachiLtd.) to expose a section perpendicular to the longitudinal direction ofthe strip-shaped LED device and showing a central LED chip, whichsection was then observed at a magnification of about 10,000 to evaluatethe degree of contact between the front and back electrodes and thelight-transmissive electroconductive layers opposite to the electrodesand the degree of filling with the elastomer on the electrodes and nearthe LED chip peripheral wall. The evaluation was performed according tothe following standard.

A: Electrodes on an LED chip and the adjacent electroconductive layerson the light-transmissive electroconductive members exhibited a contactwith each other, and the elastomer filled up the crevice gap between theunevenness on the electrodes and the opposite electroconductive layers.The elastomer filled up to the peripheral wall of the LED chip.

A2: The electrodes on a one-face electrode-type LED chip and theadjacent electroconductive layer on the light-transmissiveelectro-conductive member exhibited a contact with each other, and theelastomer filled up the crevice gap between the unevenness on theabove-mentioned electrode, and the electroconductive layer. Theelastomer filled up to the peripheral wall of the LED chip. However, theelastomer did not fill the gap between the electrode-free face of theLED chip and the adjacent transparent substrate.

B1: The electroconductive layer and the adjacent light-emitting sideelectrode of a two-face electrode-type LDE chip exhibited a contact witheach other, and the non-light-emitting side electrode and the adjacentelectroconductive layer exhibited a contact with each other. And thecircumference of the LED chip was filled up with the elastomer. Thecrevice gap between the unevenness on the non-light-emitting sideelectrode of the LED chip and the adjacent electroconductive layer wasfilled up with the elastomer. However, the crevice gap between theunevenness on the light-emitting-side electrode of the LED chip and theadjacent electroconductive layer was not filled with the elastomer.

C1: The electroconductive layer and the adjacent light-emitting sideelectrode of a two-face electrode-type LDE chip exhibited a contact witheach other, and the non-light-emitting side electrode and the adjacentelectroconductive layer exhibited a contact with each other. And thecircumference of the LED chip was filled up with the elastomer. Thecrevice gap between the unevenness on the luminescent side electrode ofthe LED chip and the adjacent electroconductive layer was filled up withthe elastomer. However, the crevice gap between the unevenness on thenonlight-emitting-side electrode of the LED chip and the adjacentelectroconductive layers was not filled with the elastomer.

C2: The electrodes on a one-face electrode-type LED chip and theelectroconductive layers on the adjacent light-transmissiveelectroconductive member contacted with each other in two pairs,respectively, and the elastomer filled up to the peripheral wall of theLED chip. However, the crevice gaps between the unevenness on theabove-mentioned electrodes and the adjacent electroconductive layers,were not filled with the elastomer.

D: Although the electrodes on an LED chip and the adjacentelectroconductive layers on the light-transmissive electro-conductivemembers exhibited a contact with each other, the crevice gaps betweenthe unevenness on the above-mentioned electrodes and the adjacentelectroconductive layers, were not filled with the elastomer, and theelastomer did not fill up to the peripheral wall of the LED chip.

Elastomer Coverage of LED Electrode Surface Two-Face Electrode-Type

A light-transmissive LED device before and after the above-mentionedflexural resistance test and thermal cycling test and having an LED chipdisposition similar to the one illustrated in FIGS. 1 and 2 wassubjected to a process including cutting-off at a longitudinal end sealportion thereof with a diamond cutter, and putting an about 5 mm-cuthorizontally into the light-transmissive elastomer layer 30 using amicrotome. Square bars made of stainless steel, having a width of 5 mm,thickness of 5 mm and a length identical to the end length of thelight-transmissive LED luminescent sheet (devices) and equipped with ahandle, was bonded firmly onto the outer surfaces at the cut end of thelight-transmissive electroconductive member 20A and 20B. A double-facepressure sensitive adhesive tape having the same size as the LED devicesample was stuck on a horizontally disposed hard plate, and the outersurface of the light-transmissive electroconductive member 20B was stuckonto the double-face adhesive tape to fix the LED device sample onto thehard plate. While being maintained horizontally, the stainless steel barbonded to light-transmissive electroconductive member 20A was pulled upslowly in a direction of 90 degrees to the light-transmissiveelectroconductive member 20B, to peel the light-transmissiveelectroconductive member 20A off the light-transmissiveelectroconductive member 20B. As a result of repeating the aboveoperations, several LED device samples with exposed surface of electrode15A of the LED chip were prepared, and a part thereof was used as asample for elastomer coverage measurement of the electrode layer 15A ofthe LED chip.

The remainder of the light-transmissive LED devices from which thelight-transmissive electroconductive member 20A had been peeled, wassubjected to application of a 180 μm-thick PET film with an adhesivesonto the surface including the exposed electrode 15A, while beingmaintained horizontally, the stainless steel bar bonded to thelight-transmissive electroconductive member 20B as mentioned above waspulled up slowly in a direction of 90 degrees to a horizontal plane, topeel the LED device sample off the hard plate. Next, the thus-peeled LEDdevice sample was turned upside down, and the outer surface of theapplied 180 μm-thick PET film was stuck onto a hard plate via adouble-face adhesive tape to fix the LED device sample onto the hardplate. Then, while being maintained horizontally, the stainless steelbar bonded to light-transmissive electroconductive member 20B was pulledup slowly in a direction of 90 degrees to the hard plate surface, topeel the light-transmissive electroconductive member 20B off the 180μm-thick PET film applied with the adhesives. As a result, the LED chipwith the surface-exposed electrode 15B was left on the PET film. Thiswas used as a sample for elastomer coverage measurement of the electrodelayer 15B of the LED chip.

One-Face Electrode-Type

Light-transmissive one-face electrode-type LED devices before and afterthe above-mentioned flexural resistance test and thermal cycling testand having an LED chip disposition similar to the one illustrated inFIG. 14 was treated in a similar manner as the former half of the abovesection for two-face electrode-type LED devices to peel only thelight-transmissive electroconductive member 20C and expose the faceincluding the electrodes 15A and 15B, thereby making samples formeasuring the elastomer coverages of the electrodes.

The elastomer coverage measurement was performed by EDX (energydispersion-type X-ray analysis) using a “NORAY System SIX” energydispersion-type X-ray spectroscopic analyzer (made by Thermo FisherScientific) attached to a field emission scanning electron microscope(“ULTRA55”, made by Carl Zeiss), including provision of anelectroconductive film of Pt—Pd on exposed electrode surfaces of theabove-prepared samples to effect elementary mapping. The analysis wasperformed by using K-ray of carbon C to determine an area (c) of carbonatom % of 50% or more and an area (d) of the electrode per se and tocalculate a ratio of c/d as an elastomer coverage.

Example 1 (Two-Face Electrode-Type LED Device)

A strip-shaped LED device having a general structure including a lengthof about 90 mm and a width of about 50 mm was prepared by disposing sixtwo-face electrode-type LED chips connected in series and arranged in astraight line with a spacing of about 5 mm from each other and disposinga pair of elastomer sheets respectively over the two faces ofelectrodes, followed by sandwiching with a pair of light-transmissiveelectroconductive member sheets and hot vacuum pressing. A partiallaminate structure thereof was similar as shown in FIGS. 1 and 2 .Details thereof are described below.

LED Chip

As LED chips, GaAlAs/GaAs-based red luminescence LED chips (planar size:about 300×300 μm, whole thickness (height):175 μm) having electrodes onboth front and back faces, were provided.

The electrode layers on both faces of each LED chip included a substrateside electrode layer (15A) comprising a 3.5 μm-thick Au layerelectrically connected to an N-type semiconductor (N-GaAlAs) layer (42)of an LED body (11) via a semiconductor substrate (41), and alight-emitting side electrode layer (15B) comprising a 0.5 μm-thick Aulayer and electrically connected to a P-type semiconductor (P-GaAlAs)layer (44) of the LED body. In the chip, the substrate side electrodelayer (15A) was formed entirely on one face of the LED body (11), andthe light-emitting side electrode layer (15B) was formed on 20% of theother face of the LED body.

In addition, in the LED chip, the substrate side electrode layer (15A)had a surface roughness Ra of 0.5 μm and the light-emitting sideelectrode layer (15B) had a surface roughness Ra of 0.13 μm.

Preparation of a Light-Transmissive Electroconductive Member

Light-transmissive electroconductive members (20A, 20B) were prepared.Each light-transmissive electroconductive member (20) was formed byprinting a slurry with ITO fine particles dispersed therein on a 180μm-thick polyethylene terephthalate (PET) sheet as a transparentsubstrate, followed by curing with ultraviolet rays at room temperatureto form a 1 μm-thick electroconductive layer and patterning thereof bylaser irradiation, to form a circuit layer (25) suitable for the seriesconnection of six LED chips arranged in a straight line as mentionedabove. The slurry comprised an ultraviolet-curable acrylic transparentresin in which ITO particulates of 0.15 μm in average particle size(aspect ratio: 3.0) were dispersed at a rate of about 90 wt. %.

Elastomer Sheet

A 60 μm-thick acrylic elastomer sheet having a Vicat softeningtemperature of 110° C. was provided as a material constituting alight-transmissive elastomer layer (30), and cut into a sheet (35) withan areal size almost the same as the light-transmissiveelectroconductive member (20). The glass transition temperature thereofwas −40° C., and the elastomer exhibited a melting temperature of 220°C., and tensile storage moduli of 1.1 GPa at 0° C., 0.3 GPa at 100° C.and 0.2 GPa at 110° C. (Vicat softening temperature).

Lamination

With reference to FIG. 7 (however, used in a state of upside down),first, a light-transmissive electroconductive member (20A) was held sothat its electric conduction circuitry layer was directed upward. Then,an elastomer sheet (35) was laminated, and also an LED chip (10) wasdisposed thereon, so that the light-emitting side electrode layer (15B)was directed upward. Next, another elastomer sheet (35) was laminated onthe light-emitting side electrode layer (15B) of the LED chip, and alsothe light-transmissive electroconductive member (20B) was laminatedthereon with its electric conduction circuitry layer (25B) directeddownward.

Preparation of a Light-Transmissive LED Luminescence Sheet

The resultant laminate was subjected to a preliminary press at apressure of 0.1 MPa, a vacuum suction of the atmosphere to 5 or lesskPa, and a vacuum hot pressing of 120° C. and 10 MPa for 10 minutes,thereby obtaining a light-transmissive LED luminescence sheet (LEDdevice) wherein the light-transmissive elastomer layer (30) was denselyformed between the light-transmissive electroconductive members(20A-20B) and surrounding the LED chip (10) without air bubbles. Theperipheral end faces of the obtained light-transmissive luminescencesheet were sealed with a thermosetting resin, to obtain a strip-shapedLED device.

The outline of the manufacturing conditions of above-mentioned Example 1is summarized and shown in Table 1 appearing hereinafter together withthe results of the following Examples and Comparative Examples.

The LED device obtained above was evaluated with respect to thethickness of the light-transmissive insulating elastomer layer,sectional observation, the elastomer coverage of the LED electrode, theflexural resistance, and the thermal cycling test. The results aresummarized and shown in Table 2 appearing hereinafter together with theresults of the following Examples and Comparative Examples.

Example 2 (Two-Face Electrode-Type)

A light-transmissive LED device was prepared and evaluated in the samemanner as in Example 1 except that the thicknesses of theelectroconductive layers of the light-transmissive electroconductivemembers both on the substrate side and the light-emitting side were bothchanged to 2 μm, the pressure and heating temperature for the vacuum hotpressing of the laminate were changed to 12 MPa and 110° C.,respectively.

Example 3 (Two-Face Electrode-Type)

A light-transmissive LED device was prepared and evaluated in the samemanner as in Example 1 except that the thicknesses of theelectroconductive layers of the light-transmissive electroconductivemembers both on the substrate side and the light-emitting side were bothchanged to 3 μm, the pressure and heating temperature for the vacuum hotpressing of the laminate were changed to 15 MPa and 100° C.,respectively.

Example 4 (Two-Face Electrode-Type)

A light-transmissive LED device was prepared and evaluated in the samemanner as in Example 1 except that the thicknesses of theelectroconductive layers of the light-transmissive electroconductivemembers both on the substrate side and the light-emitting side were bothchanged to 3 μm, and the elastomer layer thickness was changed to 80 μm.

Sectional Observation

In the light-transmissive LED luminescence sheets of the above-describedExamples, it was found that the electrode layers on the substrate sideand the light-emitting side on the front and back faces of the LED chipexhibited a contact with the electroconductive layers of thelight-transmissive electroconductive members on the substrate side andthe light-emitting side, respectively, the peripheral sides of the LEDchip were filled with the elastomer.

Further, in the light-transmissive LED luminescence sheets of theabove-described Examples, it was found that the crevice gap between thesurface unevenness on the substrate side electrode layer of the LED chipand the electroconductive layer of the light-transmissiveelectroconductive member on the substrate side was filled up with theelastomer.

Comparative Example 1 An Example Wherein an Elastomer Sheet was NotDisposed on One of Two-Face Electrodes

A light-transmissive LED device was prepared and evaluated in the samemanner as in Example 1 except that the thicknesses of theelectroconductive layers (25A, 25B) of the light-transmissiveelectroconductive members on the substrate side and the light-emittingside were both changed to 3 μm, no elastomer sheet was disposed betweenthe light-transmissive electroconductive member (20A) and the substrateside electrode layer of the LED chip, and a 120 μm-thick elastomer sheetwas disposed between the light-transmissive electroconductive member(20B) on the light-emitting side and the light-emitting side electrodelayer (15B) of the LED chip.

Flexural Resistance Test

In the light-transmissive LED luminescence sheet of this experimentalexample, one of six samples caused a lighting failure at a bendingradius of 100 mm and all of the six samples caused a lighting failure ata bending radius of 80 mm. After being released from the bending, foursamples recovered a lighting state. After 10 cycles of the flexuralresistance test, all the six samples remained in the non-lighting stateeven after being released from the bending.

Thermal Cycling Test

In the light-transmissive LED luminescence sheet of this experimentalexample, one sample caused a lighting failure after 1500 cycles, and allsix samples caused a lighting failure after 2000 cycles.

Sectional Observation

In the light-transmissive LED luminescence sheet of this experimentalexample, the substrate side electrode layer and the light-emitting sideelectrode layer on both faces of the LED chip exhibited a contact withthe electroconductive layer of the light-transmissive electroconductivemember on the substrate side electrode layer and the electroconductivelayer of the light-transmissive electroconductive member on thelight-emitting side electrode layer, respectively, and the circumferenceof the LED chip was filled up with the elastomer.

Further, in the light-transmissive LED luminescence sheet of thisexperimental example, the crevice gap between the surface unevenness onthe light-emitting side electrode layer of the LED chip and theelectroconductive layer of the light-transmissive electroconductivemember on the light-emitting side electrode layer in contact therewithwas filled up with the elastomer.

However, in the light-transmissive LED luminescence sheet of thisexperimental example, it was found that the crevice gap between thesurface unevenness on the substrate side electrode layer of the LED chipon which no elastomer layer was disposed at the time of production, andthe electroconductive layer of the light-transmissive electroconductivemember on the substrate side electrode layer in contact therewith, wasnot tilled with the elastomer.

Example 5 An Example of Disposing an Elastomer Sheet on theElectrode-Side Face of a One-Face Electrode-Type LED Chip

A strip-shaped LED device having a general structure roughly identicalto that of the device in Example 1 including a length of about 90 mm anda width of about 50 mm was prepared by disposing, however, one-faceelectrode-type LED chips connected in series and arranged in a straightline with a spacing of about 5 mm from each other and disposing anelastomer sheet over the electrodes on one side, followed by sandwichingwith a pair of light-transmissive electroconductive member sheets andhot vacuum pressing. A partial laminate structure thereof is similar asshown in FIGS. 14 and 15 . Details thereof are described below.

LED Chip

As LED chips, GaN-based blue luminescence LED chips (planar size: about350×350 μm, whole thickness (height): 175 μm) having two types ofelectrodes on one face thereof, were provided. An LED chip (10A) had astructure including a sapphire-made substrate (41A), and an N-typesemiconductor layer (42), a luminous layer (43) and a P-typesemiconductor layer (44) successively laminated in this order on thesubstrate. On one face (light-emitting face) thereof on the side of theP-type semiconductor layer (44), electrodes (15A and 15B) eachcomprising 1.5 μm-thick Au were disposed so as to be electricallyconnected with the N-type semiconductor layer (42) and the P-typesemiconductor layer (44), respectively. The electrodes 15A and 15B eachhad a surface roughness Ra of 0.15 μm.

A Light-Transmissive Electroconductive Member and a TransparentSubstrate

Similarly as in Example 1, a pair of transparent substrates (21) eachcomprising a 180 μm-thick polyethylene terephthalate (PET) sheet, wereprovided, and one of these was made a non-light-emitting-sidetransparent substrate 21D. On one surface of the other transparentsubstrate 21C, a slurry obtained by dispersing ITO particulates of 0.15μm in average particle size (aspect ratio: 3) at a rate of about 90 wt.% in an ultraviolet-curable acrylic transparent resin was applied andcured with ultraviolet rays at room temperature to form a 3 μm-thickfilm. By partial removal (patterning) of the film by laser irradiation,a light-transmissive electroconductive member 20C was provided with anelectroconductive layer 25A for connection with an electrode 15A for anN-type semiconductor and an electroconductive layer 25B for connectionwith electrode 15B for a P-type semiconductor, which electroconductivelayers 25A and 25B were suitable for the series connection of six LEDchips arranged in a straight line, as mentioned above.

Elastomer Sheet

Similarly as in Example 1, a 60 μm-thick elastomer sheet having a Vicatsoftening temperature of 110° C. was provided and cut into an areal sizecomparable to that of the light-transmissive electroconductive member20C to provide an elastomer sheet 35.

Lamination

With reference to FIG. 16 , on an electroconductive layer (25) directedupward of the light-transmissive electroconductive member 20C, first anelastomer sheet 35 was laminated, the LED chips 10A were disposedthereon so that light-emitting side electrodes 15A and 15B were directeddownward and positionally aligned opposite to the electroconductivelayers 25A and 25B, respectively, of the light-transmissiveelectroconductive member 20C to he laminated with each other. Then, atransparent substrate 21 was laminated on the nonluminescent face 71 ofthe LED chips 10A, without disposing an elastomer sheet therebetween.

Preparation of a Light-Transmissive LED Luminescence Sheet

The resultant laminate was subjected to a preliminary press at apressure of 0.1 MPa, a vacuum suction of the atmosphere to 5 or lesskPa, and a vacuum hot pressing of 120° C. and 10 MPa for 10 minutes,thereby obtaining a light-transmissive LED luminescence sheet (LEDluminescent device) wherein the light-transmissive elastomer 30 filledbetween the light-transmissive electroconductive member 20 c with thetransparent substrate 21 c and surrounding the LED chips 10A without airbubbles, to provide a light-transmissive LED luminescence sheet 1A (FIG.14 ). The peripheral end faces of the obtained light-transmissive LEDluminescence sheet were sealed with a thermosetting resin, to obtain astrip-shaped LED luminescent device, which was then evaluated in thesame manner as in Example 1.

Sectional Observation

In the light-transmissive LED luminescence sheets of the above-describedExample, it was found that the two types of light-emitting-sideelectrode layers formed on one face of the LED chip exhibited a contactwith the electroconductive layers of the light-transmissiveelectroconductive member, and the peripheral sides of the LED chip werefilled with the elastomer.

Further, in the light-transmissive LED luminescence sheets of theabove-described Example, the crevice gaps between the surface unevennesson the two types of light-emitting-side electrode layers of the LED chipand the electroconductive layers in contact therewith of thelight-transmissive electroconductive member on the substrate side werefound to be filled up with the elastomer.

The gap between the electrode-free face of the LED chip and thetransparent substrate was found to be not filled with the elastomer.

Example 6 An Example of Disposing an Elastomer Sheet on the ElectrodeSide Face of a One-Face Electrode-Type LED Chip

A light-transmissive LED luminescent device was prepared and evaluatedin the same manner as in Example 5 except that the thickness of theelastomer sheet 35 was changed to 80 μm.

Comparative Example 2 An Example of Not Disposing an Elastomer Sheet onthe Electrode-Side Face of a One-Face Electrode-Type LED Chip

A light-transmissive LED luminescent device was prepared and evaluatedin the same manner as in Example 5 except that a 60 μm-thick elastomersheet 35 was disposed not on the electrode-side face but on thesubstrate-side face of the LED chip 10A.

Flexural Resistance Test

In the light-transmissive LED luminescence sheet of this experimentalexample, one of six samples caused a lighting failure at a bendingradius of 50 mm and all of the six samples caused a lighting failure ata bending radius of 40 mm. After being released from the bending, foursamples recovered a lighting state. After 10 cycles of the flexuralresistance test, all the six samples remained in the non-lighting stateeven after being released from the bending.

Thermal Cycling Test

In the light-transmissive LED luminescence sheet of this experimentalexample, one sample caused a lighting failure after 100 cycles, and allsix samples caused a lighting failure after 500 cycles.

Sectional Observation

In the light-transmissive LED luminescence sheet of this experimentalexample, the two types of the light-emitting side electrode layers onone face of the LED chip exhibited a contact with the electroconductivelayers of the light-transmissive electroconductive member, and thecircumference of the LED chip was filled up with the elastomer.

However, in the light-transmissive LED luminescence sheet of thisexperimental example, it was found that the crevice gaps between thesurface unevenness on the two types of the light-emitting-side electrodelayers of the LED chip and the electroconductive layers in contacttherewith of the light-transmissive electroconductive member, were notfilled with the elastomer.

On the contrary, the gap between the electrode-free face of the LED chipand the transparent substrate was filled up with the elastomer.

Example 7 An Example of Disposing an Elastomer Sheet on Both Faces of aOne-Face Electrode-Type LED Chip

A light-transmissive LED luminescent device was prepared and evaluatedin the same manner as in Example 5 except that the thickness of theelastomer sheet 35 was changed to 30 μm, and such a 30 μm-thickelastomer sheet was disposed not only on the two light-emitting-sideelectrode layers of the LED chip and also between the other face of theLED chip and the transparent substrate.

Example 8 An Example Wherein an Elastomer Sheet was Disposed on BothFaces of a Two-Face Electrode-Type LED Chip and the ElectroconductiveLayer was Formed by Sputtering

A light-transmissive LED luminescent device was prepared and evaluatedin the same manner as in Example 1 except for using a light-transmissiveelectroconductive member obtained by forming not a coated-and-curedslurry type electroconductive layer but a 0.15 μm-thick ITO sputteredfilm as an electroconductive layer on the 180 μm-thick PET sheet.

Example 9 An Example Wherein an Elastomer Sheet was Disposed on BothFaces of a Two-Face Electrode-Type LED Chip and the ElectroconductiveLayers were Formed by Sputtering

A light-transmissive LED luminescent device was prepared and evaluatedin the same manner as in Example 8 except that a 45 μm-thick elastomersheet having a Vicat softening temperature of 140° C. was used, and thevacuum hot pressing was performed at 140° C.

Comparative Example 3 An Example Wherein an Elastomer Sheet was Disposedon One Face of a Two-Face Electrode-Type LED Chip and theElectroconductive Layers were Formed by Sputtering

A light-transmissive LED luminescent device was prepared and evaluatedin the same manner as in Example 8 except that light-transmissiveelectroconductive members were prepared by forming electroconductivelayers by sputtering similarly as in Example 8, and a 100 μm-thickelastomer sheet was disposed only on the light-emitting-side face andnot on the non-light-emitting side face of the LED chip.

Flexural Resistance Test

In the light-transmissive LED luminescence sheet of this experimentalexample, one of six samples caused a lighting failure at a bendingradius of 100 mm and all of the six samples caused a lighting failure ata bending radius of 80 mm. After being released from the bending, foursamples recovered a lighting state. After 10 cycles of the flexuralresistance test, all the six samples remained in the non-lighting stateeven after being released from the bending.

Thermal Cycling Test

In the light-transmissive LED luminescence sheet of this experimentalexample, one sample caused a lighting failure after 50 cycles, and allsix samples caused a lighting failure after 500 cycles.

Sectional Observation

In the light-transmissive LED luminescence sheet of this experimentalexample, the two types of electrode layers on both faces of the LED chipexhibited a contact with the electroconductive layers of thelight-transmissive electroconductive members, and the circumference ofthe LED chip was filled up with the elastomer.

However, in the light-transmissive LED luminescence sheet of thisexperimental example, it was found that the crevice gap between thesurface unevenness on the nonlight-emitting-side electrode layer of theLED chip and the electroconductive layer in contact therewith of thelight transmissive electroconductive member was not filled with theelastomer.

On the other hand, the gap between the luminescence face of the LED chipand the transparent substrate was filled up with the elastomer.

Example 10 An Example Wherein an Elastomer Sheet was Disposed on BothFaces of a One-Face Electrode-Type LED Chip and the ElectroconductiveLayers were Formed by Sputtering

A light-transmissive LED luminescent device was prepared and evaluatedin the same manner as in Example 7 except that a light-transmissiveelectroconductive member was prepared by forming electroconductivelayers by sputtering similarly as in Example 8.

Comparative Example 4 An Example Wherein an Elastomer Sheet was NotDisposed on the Electrode Face of a One-Face Electrode-Type LED Chip andthe Electroconductive Layers were Formed by Sputtering

A light-transmissive LED luminescent device was prepared and evaluatedin the same manner as in Comparative Example 2 except that alight-transmissive electroconductive member was prepared by formingelectroconductive layers by sputtering similarly as in Example 8.

Flexural Resistance Test

In the light-transmissive LED luminescence sheet of this experimentalexample, two of six samples caused a lighting failure at a bendingradius of 50 mm and all of the six samples caused a lighting failure ata bending radius of 40 mm. Even after being released from the bending, 5samples did not recover a lighting state.

Thermal Cycling Test

In the light-transmissive LED luminescence sheet of this experimentalexample, one sample caused a lighting failure after 100 cycles, and allsix samples caused a lighting failure after 500 cycles.

Example 11 An Example Wherein an Elastomer Sheet was Disposed on theElectrode Face of a One-Face Electrode-Type LED Chip and theElectroconductive Layers were Formed by Sputtering

A light-transmissive LED luminescent device was prepared and evaluatedin the same manner as in Example 5 except that a light-transmissiveelectroconductive member was prepared by forming electroconductivelayers by sputtering similarly as in Example 8.

Examples 12, 15 and 16

Light-transmissive LED luminescent devices were prepared and evaluatedin the same manner as in Example 5 except that the thicknesses of theelectroconductive layers of light-transmissive electroconductive memberswere changed to 5 μm, 0.5 μm and 12 μm, respectively.

In the flexural resistance test, the light-transmissive LED luminescencesheets of all these Examples exhibited a result that all the six samplesretained the lighting state of the LED chips at bending radii down to 30mm.

In the thermal cycling test, the light-transmissive LED luminescencesheets of all these Examples exhibited a result that all the six samplesretained the lighting state of the LED chips even after 2500 cycles.

Examples 13 and 14

Light-transmissive LED luminescent devices were prepared and evaluatedin the same manner as in Example 1 except that the thicknesses of theelectroconductive layers were changed to 0.5 μm and 12 μm, respectively.

Example 17

Silver halide as a photosensitive compound was applied on a 180 μm-thickPET sheet, exposed and developed to provide a light-transmissiveelectroconductive member having a square lattice-shaped Ag particle meshelectrode layer with a thickness of 1 μm, a line diameter of 10 μm andan opening of 500 μm as a light-transmissive electroconductive layer.

A light-transmissive LED luminescent device was prepared and evaluatedin the same manner as in Example 1 except for using thelight-transmissive electroconductive member instead of thelight-transmissive electroconductive member having an ITO-dispersed andcured resin film-type light-transmissive electroconductive

Example 18

A light-transmissive LED luminescent device was prepared and evaluatedin the same manner as in Example 5 except for using thelight-transmissive electroconductive member used in Example 17 insteadof the light-transmissive electroconductive member having anITO-dispersed and cured resin film-type light-transmissiveelectroconductive layer.

Comparative Example 5 An Example Wherein Two-Face Electrode-Type LEDChips were Disposed in Through-Holes Provided in an Elastomer Sheet

A light-transmissive LED luminescence sheet was prepared by a processdisclosed in Patent document 5.

LED Chip

Elastomer sheets having a Vicat softening temperature of 110° C.similarly as those used in Example 1 but having a thickness of 120 μmwere used to form strip-shaped elastomer sheets with a planar shapeidentical to those used in Example 1, which were then bored to form sixthrough-holes each suitable for accommodating six LED chips therein.Elastomer sheets thus formed were disposed to accommodate six LED chipsdisposed in series within the through-holes, and were thereaftersubjected to hot vacuum pressing to prepare a light-transmissive LEDluminescence sheet, similarly as in Example 1.

Flexural Resistance Test

In the light-transmissive LED luminescence sheet of this experimentalexample, all six samples caused a lighting failure at bending radii downto 100 mm.

Thermal Cycling Test

In the light-transmissive LED luminescence sheet of this experimentalexample, one sample caused a lighting failure after 500 cycles, and allsix samples caused a lighting failure after 550 cycles.

Sectional Observation

In the light-transmissive LED luminescence sheet of this experimentalexample, the substrate-side electrode layer and the light-emitting sideelectrode layer on both faces of the LED chip exhibited a contact withthe electroconductive layers of the light-transmissive electroconductivemembers on the substrate side and the light-emitting side, and thecircumference of the LED chip was filled up with the elastomer.

However, in the light-transmissive LED luminescence sheet of thisexperimental example, it was found that neither the crevice gap betweenthe surface unevenness on the substrate-side electrode layer of the LEDchip and the electroconductive layer in contact therewith of thelight-transmissive electroconductive member, nor the crevice gap betweenthe surface unevenness on the light-emitting-side electrode layer of theLED chip and the electroconductive layer in contact therewith of thelight--transmissive electroconductive member, was filled with theelastomer.

Comparative Example 6 An Example Wherein the Circumference of a One-FaceElectrode-Type LED Chip was Filled Up with an Adhesive

A light-transmissive LED luminescence sheet was produced by a processdisclosed in Patent document 4.

LED Chip

LED chips, a strip-shaped light-transmissive electroconductive memberand a strip-shaped transparent substrate, all identical to those used inExample 5, were used.

Lamination

Description is made by using reference symbols shown in FIG. 16 . Alight-transmissive electroconductive member 20C was held so thatelectroconductive layers 25A and 25B were directed upward, and thereon,the LED chips 10A were disposed so that their two types of electrodelayers 15A and 15B as luminescence-side electrode layers were directeddownward and aligned with electroconductive layers 25A and 25B,respectively, and fixed with each other with an anisotropicelectroconductive adhesive. Then, a transparent substrate 21D waslaminated over electrode-free upper faces of the LED chips 10A.

Production of a Light-Transmissive LED Luminescence Sheet

The resultant laminate was placed under a vacuum of 5 kPa or below, andan ultraviolet-curable acrylic resin-based adhesive was injected betweenthe light-transmissive electroconductive member 20C and the transparentsubstrate 21D, and around the LED chips 10A, so as not to leave gaps.Then, the ultraviolet-curable acrylic resin-based adhesive was partiallycured by irradiation with ultraviolet rays.

As a result, there was obtained a light-transmissive LED luminescencesheet, as a luminescent device having a flexural resistance andincluding the surfaces of the LED chip 10A, other than electrode layers15A and 15B, bonded with the light-transmissive electroconductive memberand the transparent substrate. The end faces of the light-transmissiveLED luminescence sheet were sealed with a thermosetting resin, to obtaina strip shaped LED luminescent device, which was then evaluated in thesame manner as in Example 5.

Flexural Resistance Test

In the light-transmissive LED luminescence sheet of this experimentalexample, all six samples caused a lighting failure at bending radii downto 60 mm.

Thermal Cycling Test

In the light-transmissive LED luminescence sheet of this experimentalexample, one sample caused a lighting failure after 60 cycles, and allsix samples caused a lighting failure after 600 cycles.

Sectional Observation

In the light-transmissive LED luminescence sheet of this experimentalexample, the two types of the light-emitting side electrode layers onone face of the LED chip exhibited a contact with the electroconductivelayers of the light-transmissive electroconductive member, and thecircumference of the LED chip was filled up with the elastomer.

However, in the light-transmissive LED luminescence sheet of thisexperimental example, it was found that neither the crevice gap betweenthe surface unevenness on the substrate-side electrode layer of the LEDchip and the electroconductive layer in contact therewith of thelight-transmissive electroconductive member, nor the crevice gap betweenthe surface unevenness on the light-emitting-side electrode layer of theLED chip and the electroconductive layer in contact therewith of thelight-transmissive electroconductive member, was filled with the acrylicresin-based adhesive.

Comparative Example 7 An Example Wherein a Hot Melt Adhesive Sheet wasDisposed over Both Faces of Two-Face Electrode-Type LED Chips

A strip-shaped LED luminescent device was prepared and evaluated in thesame manner as in Example 1 except for disposing a commerciallyavailable 60 μm-thick hot melt adhesive sheet having a softeningtemperature of 120° C. as measured by a ring and ball method (JISK7234), instead of the elastomer sheet, over both faces of the LED chipsto form a laminate; and subjecting the laminate to 1 minute of pressingat a pressure of 100 kgf/cm² in an environment of atmospheric pressureand a temperature of 180° C., to provide a light-transmissive LEDluminescent sheet.

Flexural Resistance Test

In the light-transmissive LED luminescence sheet of this comparativeexample, all six samples retained a lighting state down to a bendingradius of 60 mm but caused a lighting failure at a bending radius of 30mm.

Thermal Cycling Test

In the light-transmissive LED luminescence sheet of this experimentalexample, all six samples caused a lighting failure after 600 cycles.

Sectional Observation

In the light-transmissive LED luminescence sheet of this comparativeexample, almost no adhesive was found to be present in the crevice gapbetween the surface unevenness on the substrate-side electrode layer ofthe LED chip and the electroconductive layer in contact therewith of thelight-transmissive electroconductive member, or the crevice gap betweenthe surface unevenness on the light-emitting-side electrode layer of theLED chip and the electroconductive layer in contact therewith of thelight-transmissive electroconductive member.

Comparative Example 8

With reference to FIG. 9 , a light-transmissive LED luminescent sheetwas prepared and evaluated in the same manner as in Example 1 except forchanging both the thickness of the electroconductive layer (25A) of thelight-transmissive electroconductive member on the substrate-sideelectrode layer and the thickness of the electroconductive layer (25B)of the light transmissive electroconductive member on thelight-emitting-side electrode layer to 3 μm, omitting the disposition ofan elastomer sheet between the light-transmissive electroconductivemember on the light-emitting surface and the light-emitting surface-sideelectrode layer (15B) of the LED chip, and changing the thickness of theelastomer sheet (35) disposed between the light-transmissiveelectroconductive member (25A) on the substrate-side electrode layer andthe substrate-side electrode layer (15A) of the LED chip to 120 μm.

Flexural Resistance Test

In the light-transmissive LED luminescence sheet of this experimentalexample, one of six samples caused a lighting failure at a bendingradius of 100 mm and all of the six samples caused a lighting failure ata bending radius of 80 mm. After being released from the bending, foursamples recovered a lighting state. After 10 cycles of the flexuralresistance test, all the six samples remained in the non-lighting stateeven after being released from the bending.

Thermal Cycling Test

In the light-transmissive LED luminescence sheet of this experimentalexample, one sample caused a lighting failure after 1500 cycles, and allsix samples caused a lighting failure after 2000 cycles.

Sectional Observation

In the light-transmissive LED luminescence sheet of this experimentalexample, the substrate side electrode layer and the light-emitting sideelectrode layer on both faces of the LED chip exhibited a contact withthe electroconductive layer of the light-transmissive electroconductivemember on the substrate side electrode layer and the electroconductivelayer of the light-transmissive electroconductive member on thelight-emitting side electrode layer, respectively, and the circumferenceof the LED chip was filled up with the elastomer.

Further, in the light-transmissive LED luminescence sheet of thisexperimental example, the crevice gap between the surface unevenness onthe light-emitting side electrode layer of the LED chip and theelectroconductive layer of the light-transmissive electroconductivemember on the side of the light-emitting side electrode layer in contacttherewith was filled up with the elastomer.

However, in the light-transmissive LED luminescence sheet of thisexperimental example, it was found that the crevice gap between thesurface unevenness on the substrate side electrode layer of the LED chipon which no elastomer layer was disposed at the time of production, andthe electroconductive layer of the light-transmissive electroconductivemember on the substrate side electrode layer in contact therewith, wasnot filled with the elastomer.

With respect to the above-mentioned Examples and Comparative Examples,the outline of the production conditions are summarized in Table 1 andthe evaluation results are collectively shown in Table 2, respectively.

TABLE 1 Disposed on lower face (*1) of LED. Transmissive conductive LEDmember Electrode Conductive Elastomer Two Height (μm) (*4) Substratelayer sheet (*3) elctrodes Lower Upper Whole Thickness ThicknessThickness on one or face face thickness Example (μm) (μm) (μm) two faces*1 *2 (μm)  1 180 1 60 two faces 0.5 3.5 175  2 180 2 60 two faces 0.53.5 175  3 180 3 60 two faces 0.5 3.5 175  4 180 3 80 two faces 0.5 3.5175  5 180 3 60 one face 1.5 — 90  6 180 3 80 one face 1.5 — 90  7 180 130 one face 1.5 — 90  8 180 0.15 60 two faces 0.5 3.5 175  9 180 0.15 45two faces 0.5 3.5 175 10 180 0.15 30 one face 1.5 — 90 11 180 0.15 60one face 1.5 — 90 12 180 5 60 one face 1.5 — 90 13 180 0.5 60 two faces0.5 3.5 175 14 180 12 60 two faces 0.5 3.5 175 15 180 0.5 60 one faces1.5 — 90 16 180 12 60 one face 1.5 — 90 17 180 1 60 two faces 0.5 3.5175 18 180 1 60 one face 1.5 — 90 Comp. 1 180 3 120  two faces 0.5 3.5175 Comp. 2 180 3 — one face 1.5 — 90 Comp. 3 180 0.15 100  two faces0.5 3.5 175 Comp. 4 180 0.15 — one face 1.5 — 90 Comp. 5 *6 180 3 — twofaces 0.5 3.5 175 Comp. 6 *7 180 3 — one face 1.5 — 90 Comp. 7 *8 180 3  60*⁵ two faces 0.5 3.5 175 Comp. 8 180 3 — two faces 0.5 3.5 175Disposed on upper face (*2) of LED. Transmissive conductive memberElastomer Conductive Property of conductor member sheet (*3) Substratelayer Sheet Total light Thickness Thickness Thickness ConductiveResistivity transmittance Haze (μm) (μm) (μm) layer (Ω/□) (%) (%)  1 60180 1 ITO 180 86 1.2 dispersed  2 60 180 2 ITO 90 83 1.5 dispersed  3 60180 3 ITO 40 83 1.5 dispersed  4 80 180 3 ITO 40 83 1.5 dispersed  5 —180 — ITO 40 83 1.5 dispersed  6 — 180 — ITO 40 83 1.5 dispersed  7 30180 — ITO 180 86 1.2 dispersed  8 60 180 0.15 ITO 50 85 1.1 dispersed  945 180 0.15 ITO 50 85 1.1 dispersed 10 30 180 — ITO 50 85 1.1 dispersed11 — 180 — ITO 50 85 1.1 dispersed 12 — 180 — ITO 30 75 2.5 dispersed 1360 180 0.5 ITO 1500 86 0.8 dispersed 14 60 180 12 ITO 30 48 10 dispersed15 — 180 — ITO 1500 86 0.8 dispersed 16 — 180 — ITO 30 48 10 dispersed17 60 180 1 Ag mesh 10 82 2.5 18 — 180 1 Ag mesh 10 82 2.5 Comp. 1 — 1803 ITO 40 83 1.5 dispersed Comp. 2 60 180 — ITO 40 83 1.5 dispersed Comp.3 — 180 0.15 ITO 50 85 1.1 dispersed Comp. 4 60 180 — ITO 50 85 1.1dispersed Comp. 5 *6 — 180 3 ITO 40 83 1.5 dispersed Comp. 6 *7 — 180 3ITO 40 83 1.5 dispersed Comp. 7 *8   60*⁵ 180 — ITO 40 83 1.5 dispersedComp. 8 120  180 3 ITO 40 83 l.5 dispersed (*1) Disposed on a lower facein FIG. 2 (two-face electrode-type LED), on a lower face in FIGS. 15 and16 (one-face electrode-type LED). Light-emitting side in either case.(*2) Disposed on an upper face in FIG. 2 (two-face electrode-type LED),on on an upper face in FIGS. 15 and 16 (one-face electrode-type LED),Non-light-emitting side in either case. (*3) A light-transmissivethermoplastic elastomer layer (*4) Height above the LED chip body*⁵Thickness (μm) of a hot melt adhesive sheet *6 LED was dispoded in athrough-hole of an elastomer sheet. *7 Bonded with an an isotropicconductive adhesive. *8 A hot melt adhesive sheet was sandwiched betweenLED electrodes and opposite electroconductive layers.

TABLE 2 Number of lighting samples Elastomer Flexural resistance afterthermal cycling test Coverage Appearance & Number of Number of AfterAfter After On On Sectional samples Minimum lighting 2000 2500 3000Total Electrode Electrode observation Bending lighting bending samplescyclesr cycles cycles thickness 15A 15B Sectional Radius (piece/ radius(piece/ (piece/ (piece/ (piece/ Example (μm) (%) (%) AppearanceObservation (mm) piece) (mm) piece) piece) piece) piece) 1 120 48 65 A A30 6/6 20 6/6 6/6 6/6 6/6 2 120 35 56 A A 30 6/6 20 6/6 6/8 6/6 6/6 3120 32 53 A A 30 6/6 20 6/6 6/6 6/6 6/6 4 160 6? 80 A A — — 20 6/6 — —6/6 5 60 62 74 A A 30 6/6 20 6/6 6/6 6/6 6/6 6 60 25 43 A  A2 — — 20 6/6— — 6/6 7 80 18 34 A A — — 20 6/6 — — 6/6 8 120 69 78 A A 40 6/6 20 4/66/6 4/6 3/6 9 90 54 64 B  B1 40 6/6 20 3/6 6/6 — 3/6 10 60 23 29 A A 406/6 20 3/6 6/6 — 2/6 11 60 72 63 A A 40 8/6 30 5/6 6/6 5/6 2/6 12 60 6274 A A 30 6/6 20 6/6 6/6 6/6 6/6 13 120 48 65 A A 30 6/6 20 4/6 6/6 6/64/6 14 120 48 65 A A 30 6/6 20 5/6 6/6 6/6 5/6 15 60 62 74 A A 30 6/6 205/6 6/6 4/6 4/6 16 60 82 74 A A 40 6/6 20 4/6 6/6 5/6 5/6 17 120 48 65 AA 30 6/6 20 6/6 6/6 6/6 6/6 18 60 62 74 A A 30 8/6 20 6/6 6/6 6/6 6/6Comp. 1 120 7 78 B  C1 100 5/6 80 0/6 0/6 — — Comp. 2 60 2 4 B  C2 505/6 40 0/6 0/6 — — Comp. 3 100 3 67 C  C1 100 5/6 80 0/6 0/6 — — Comp. 460 3 5 C  C2 50 4/6 40 0/6 0/6 — — Cemp. 5 120 2 3 C D — — 100 0/6 0/6 —— Comp. 6 15* 2 4 C D 60 0/6 — — — — — Comp. 7 120*2 12 9 C D 60 6/6 300/6 0/6 — — Comp. 8 120 75 6 B  B1 100 5/6 80 0/6 0/6 — — * 1 Thickness(μm) of adhesive layer *2Thickness (μm) of hot melt adhesive layer

In the above, although some embodiments of the present invention havebeen described, these embodiments are presented merely as an example andare not intended to limit the scope of the invention. These novelembodiments can be practiced in various other forms and can be subjectedto various omission, replacement and modification. These embodiments andmodifications thereof are included in the scope and gist of theinvention, and they are included in the invention recited in the claims,and equivalents thereof.

Industrial Applicability

As mentioned above, the present invention provides a light-emittingdevice which is excellent in flexural resistance and thermal cyclecharacteristic and can maintain a lighting state in resistance to strongbending and heat load, through a production process characterized byvacuum pressing at a temperature around or slightly above the Vicatsoftening temperature of a light-transmissive elastomer.

Description of Notations

1, 1A, 1B, 90, 90A: Light-emitting device

10: LED Chip (Two-face Electrode-type), 10A LED chip (One-faceElectrode-type)

11: LED body (Two-face Electrode-type), 11A LED body (One-FaceElectrode-type)

13: Circumference of LED Chip

15: Electrode Layer

15A: First electrode layer (cathode layer, electrode layer)

15B: Second electrode layer (anode layer, electrode layer)

17: Peripheral Face of Electrode Layer

18: Edge of Electrode Layer

20: Light-transmissive Electroconductive Member

20A: First light-transmissive electroconductive member

20B: Second light-transmissive electroconductive member

20C: Light-transmissive electroconductive member of a second embodiment

21, 21A, 21B, 21C, 21D: Transparent substrate

25: Light-transmissive Electroconductive Layer

25A: First light-transmissive electroconductive layer(light-transmissive electroconductive layer)

25B: Second light-transmissive electroconductive layer(light-transmissive electroconductive layer)

26: Surface of Light-transmissive Electroconductive Layer

30: Light-transmissive Elastomer Layer

35: Temporary Light-transmissive-Elastomer Layer

36, 36A, 36B: Bump electrode

36S: Au bump

41: LED Semiconductor Substrate (Two-face Electrode-type)

41A: LED heat-resistant board (One-face electrode-type)

42: N-type Semiconductor Layer

44: P-type Semiconductor Layer

43: Luminescent Layer

45: Unevenness

46: Concavity

47: Convexity

48: Crevice gap

71: Face of LED Body

71A: First face of LED body

71B: Second face of LED body

71C: Third face of LED body

71D: Fourth face of LED body

72: N-type Semiconductor Luminescent Layer-side Boundary

85: Light-emitting face

91: Opening

92: Crack

95: Fixing resin for sectional observations

1.-20. (canceled)
 21. A light-emitting device, comprising: a firstflexible member; a second flexible member; a circuit pattern disposed onthe first flexible member; one or more light-emitting elements locatedbetween the first flexible member and the second flexible member, eachlight-emitting element comprising an anode electrode layer and a cathodeelectrode layer, the anode electrode layer being electrically connectedto a first portion of the circuit pattern, the cathode electrode layerbeing electrically connected to a second portion of the circuit pattern;and a transparent resin located between the first flexible member andthe second flexible member, and surrounding the one or morelight-emitting elements.
 22. The light-emitting device according toclaim 21, wherein a light transmittance of the first flexible member isnot less than 1% and not more than 80%.
 23. The light-emitting deviceaccording to claim 21, wherein a light transmittance of the secondflexible member is not less than 1% and not more than 80%.
 24. Thelight-emitting device according to claim 21, wherein at least one of thefirst flexible member or the second flexible member comprises at leastone type of resin selected from the group consisting of polyethyleneterephthalate, polyethylene naphthalate, polycarbonate, polyethylenesuccinate, arton, and acrylic.
 25. The light-emitting device accordingto claim 21, wherein the one or more light-emitting elements comprise aplurality of light-emitting elements that are electrically connected tothe circuit pattern.
 26. The light-emitting device according to claim21, wherein a thickness of each light-emitting element is not less than90 μm and not more than 290 μm, in a direction from the first flexiblemember to the second flexible member.
 27. The light-emitting deviceaccording to claim 21, wherein a thickness of the first flexible memberis not less than 50 μm and not more than 300 μm.
 28. The light-emittingdevice according to claim 21, wherein a thickness of the second flexiblemember is not less than 50 μm and not more than 300 μm.
 29. Thelight-emitting device according to claim 21, wherein the circuit patterncomprises at least one type of metal selected from the group consistingof gold, silver, and copper.
 30. The light-emitting device according toclaim 21, wherein a part of the transparent resin is located between thesecond flexible member and the one or more light-emitting elements. 31.A light-emitting device, comprising: a first member; a second member; acircuit pattern disposed on the first member; one or more light-emittingelements located between the first member and the second member, eachlight-emitting element comprising an anode electrode layer and a cathodeelectrode layer, the anode electrode layer being electrically connectedto a first portion of the circuit pattern, the cathode electrode layerbeing electrically connected to a second portion of the circuit pattern;and a transparent resin located between the first member and the secondmember, and surrounding the light-emitting element; wherein: a lighttransmittance of at least one of the first member or the second memberis not less than 1% and not more than 80%.
 32. The light-emitting deviceaccording to claim 31, wherein a light transmittance of each of thefirst member and the second member is not less than 1% and not more than80%.
 33. The light-emitting device according to claim 31, wherein atleast one of the first member or the second member comprises at leastone type of resin selected from the group consisting of polyethyleneterephthalate, polyethylene naphthalate, polycarbonate, polyethylenesuccinate, arton, and acrylic.
 34. The light-emitting device accordingto claim 31, wherein the one or more light-emitting elements comprise aplurality of light-emitting elements that are electrically connected tothe circuit pattern.
 35. The light-emitting device according to claim31, wherein a thickness of each light-emitting element is not less than90 μm and not more than 290 μm, in a direction from the first member tothe second member.
 36. The light-emitting device according to claim 31,wherein a thickness of the first member is not less than 50 μm and notmore than 300 μm.
 37. The light-emitting device according to claim 31,wherein a thickness of the second member is not less than 50 μm and notmore than 300 μm.
 38. The light-emitting device according to claim 31,wherein the circuit pattern comprises at least one type of metalselected from the group consisting of gold, silver, and copper.
 39. Thelight-emitting device according to claim 31, wherein a part of thetransparent resin is located between the second member and the one ormore light-emitting elements.
 40. The light-emitting device according toclaim 31, wherein the first member and the second member are flexible.